Measuring case head expansion

I've never ventured far or often from published data so never felt the need to do this.Now I'm boldly going where [except for Bigstick etal] noone has gone before.Do I measure just fwd of the rim? 257A.I is the cartridge.I want to try some slower powders to fill the case up.I have a chrono and digital mic.

You need to measure just ahead of the web. I don't know why, and I don't know if I believe it, but one of my loading manuals, I forget which one, says you need a blade style micrometer. I think any that measures .0001" would do.

Gene, There was a lot about case head expansion written in the past in Handloader, especially by Bob Hagel. I believe he polished two dimetrically opposed spots on the rim and considered ANY increase in rim diameter excessive. I have gotten by for a long time by measuring the expansion ring ahead of the web with a .0001" mike (regular flat anvil type is OK) and considering any load that expands the brass (same brass) as much as a factory load to be maximum. I wind up with safe loads, factory or better ballistics and long case life. With the .257 AI I guess I would start with factory plus P loads and then load the formed improved cases to the same expansion. Don't know if the factory loads would produce the same pressure and expansion in the improved chamber. (Please report on this point when you know). If that didn't work I guess I would resort to the old fashioned way-as long as extraction is OK and primer pockets stayed tight for several firings I would call it good. One thing I have heard from several guys loading AI cartridges is work up to Ackley's loads carefully! curmudgeon

Much obliged to both of you.I get too many split necks,Curmudgeon, when I fire form factory loads.I will use my fire forming load which is close to fact. as a base and follow your advice from there. I'll report what I see.Probably be a week or so.[This message has been edited by gene williams (edited March 21, 2001).]

I was wrong about where to measure. One measures on the solid part of the web. Also, I couldn't use my flat anvil micrometer on .30-30 case, because the bulge ahead of the web interfered with the reading. It looks like the .30-30 cases require a blade style.

If you can get hold of a copy of "Ken Waters Pet Loads" he explains in detail how he measures case expansion, it is worth a read, and if you don't have a copy of those books, they are a good investment.IMHO.

For decades, I defended the notion of miking cases to get an idea of the internal pressures being developed. I'm the editor who originally published both Bob Hagel's and Ken Waters' articles on how they do it. I also published Waters' "Pet Loads" article as a supplement for his Pet Loads book.At the time, Waters and I both considered Hagel's method extremely risky. I still do (because it IS!). I supported Waters' more moderate approach. I've since learned how foolish and unreliable any variation of this basic technique is.� Many cases don't expand enough, even at 80,000 lb/sq in., to warn of risky or excessive pressures.� Catastrophic failures of overloaded rifles may occur with either the first over-hot round, or they may occur only after years of repeated use of over-hot loads. In the latter type of failure, the rifle has appeared "safe" with these loads, clear up until the time one round "caused" the failure "for no apparent reason."� Cases work-harden in use. Repeated use makes them become brittle in the crucial portion exposed in the breech � typically 0.200 inch of the head of the case. Cases already too hard to show "excessive" expansion here (some, even at 80,000 lb/sq in.) are especially likely to become brittle in repeated firings and reloadings, and spew wild gas and bits of brass into a shooter's face. I have on hand now a rifle utterly demolished when half the head of the case blew back through the action. The rest of the case is still in the apparently unharmed barrel, but the receiver is in many pieces, and my friend still has one piece of brass in his face (a larger chunk was surgically removed).� The maximum safe limit for many rifles and cartridges is well below the level of peak pressures that many cases can handle without any discernible or measurable indication of excess.� The less experienced you are in the use of this method, the greater is the certainty that miking your cases will inevitably lead you to accept dangerously high pressures as "safe."Careful lab tests of many typical "pet" loads, developed by attention to traditionally accepted "signs" of pressure, have shown their peak pressures to be 70,000 to 75,000 lb/sq in. The highest SAAMI "safe" pressure I know of, for any cartridge or rifle, is 65,000 lb/sq in. Most are lower. Many are much lower.Some carefully lab-tested loads, developed by miking case rims, webs, and expansion rings, have developed 80,000 lb/sq in. without measurable expansion.Stay well below the maximum charges listed in the manuals, and you'll be worlds safer without significant sacrifice in down-range performance. No micrometer is a reliable pressure gauge.

much obliged, KEN.

Great advice Ken.One question though, how do go about determining the stopping point when doing some load work with wildcats where there's a obvious lack of published data?Thks.....Ray

Since we are open again for questions- and the last one was a good one- it seems we are dealing with two different deals here, at least the airplane engineers I work with would say so.[ I aint gonna ask them cause we aint talking airplanes here,and besides, they dont always get them right !!] Anyhow, one case ,the more or less instant catastropic failure due to a load which stretches the action or barrel steel beyond its elastic limits,and the other which takes place over time from repeated applications of loads which exceed the design limits resulting in fatigue type failure.I understand that predicting fatigue failure requires something like strain gage data developed from several applications of the load.Has any one developed this data? So far this represents about 15 min. typing for me

so if I remember what I was going to ask it's a miracle. Is strain gaging chambers the most reliable method of determining pressures?If not, then what is?

"Is strain gaging chambers the most reliable method of determining pressures?"No � it's just the most reliable field method economical enough and practical enough to be available to us ol' boneheads out here. �o)

Dr. Howell,Just to satisfy my curiosity, what caliber and what type of action was involved in the failure which resulted in your friend becoming a brass head? And, what did he do wrong? Thanks CAT

"what caliber and what type of action was involved in the failure which resulted in your friend becoming a brass head? And, what did he do wrong?"� .220 Howell� FN Mauser action� Got load data for x grains of bullet A and powder B, dropped his charge back to y grains (x grains minus 5% to 10%), and loaded bullet A with that charge of powder C � because the designations of the two powders were so nearly the same that he mistook one for the otherThat reduced charge would've produced peak pressures somewhere around 44,000 to 48,000 lb/sq in., as well as I remember, if he'd used the correct powder. With the other powder, it produced pressures estimated at around 100,000 lb/sq in. Both powders are from the same manufacturer, in identical containers except for the details on their labels, with designations that begin with the same few characters.Considering the talent that so many of our crowd here and earlier present have exhibited in imaginatively mangling the spellings of familiar product names and designations used in these posts, his easy misreading of two very similar powder designations shouldn't surprise anyone here.He has graciously contributed the remains to the Powley-Howell collection of educational ballistics paraphernalia to be displayed at the Powley Center (as well as in my home and possibly on my gun-show table). In due course, I'll photograph all the recovered pieces (except those from his face!) from several angles and camera distances and make the photos available by e-mail as *.jpg files for anyone who'd like to study 'em.This case is especially useful because we KNOW all the details of the cause and therefore don't have to interpret anything from the evidence, render an opinion, or think up a bunch of possible causes.[This message has been edited by Ken Howell (edited April 14, 2001).]

Gene/ On standard cases, without the use of a blade micrometer, it helps to file two flats opposite each other on the rim. This allows you to measure the web ,just in front of the extraction groove. A small 6" file works fine as only one or two thou.,have to be removed. On magnum cases, measuring on the belt, at the exact spot each time ,works fine. Rimmed cases require a blade mic. After filing the flats,measure in the same spot each time. I've never run into any extraction problems, but you may want to reserve these filed cases for target, rather than hunting. I know some people regard this method of load development to be no better then some form of Voo-Doo, but Speer's load manual #12, and earlier I believe touch on this subject. Page 55. They do not have pressure barrels for every round they give load data for. They start with once fired cases, and retire them after the third firing for load development.After this they become work hardened, and readings are not as acurate. It is stated that between .0003" and .0005" expansion, with typical cases ,is in the pressure range of 50,000 C.U.P. It has been my experience that measuring case head expansion ,combined with a chrono- graph, that maximum loads are achieved ,long before any pressure signs are visible to the naked eye. No ejector marks, stiff bolt lift flat primers, etc. On some loads ,the expansion readings dictate to cease and desist, long before reaching load manual max. IMO, unless you are working with brass that has been work hardened, or a lot that is extemely hard, the precision micrometer(5 digit or more) will pick up case expansion way before any visible expansion shows. Including blown recievers. I would also like to add that I am not stating that any reloading method to be safe. Without the use of modern pressure testing equipment, this feature of measuring case head expansion is just one more method of trying to keep your loads safe. Even if one did have the strain guage, who is to say this would be safe without having a second or third instrument to cross check the numbers ? I know if I invest in an Oehler PBL ,I will still measure my case heads, just to see if the pressure readings are honest. This method is very slow and time consuming, but IMO, well worth it in the end One more example ,is even with proper pressure testing equipment, proving the load should be safe in a rifle, if the case expansion is exsessive, this would lead to loose primer pockets and short case life, even if the pressures were within the safe guide lines. Given the quality ammo available today, if one isn't getting at least 7 or 8 loadings, or more from say ,a magnum round, than what is the purpose of reloading in the first place? Hope this helps. Good Luck

There is an alternative method with which I have had very good results.This is the software program Quickload.Quite sophisticated and surpringly accurate and will give you pressure readings for particular loads.Being unable to afford the Oehler pressure testing equipment I tried the Quickload and am very pleased.Regards,Frank.

Frank/ Yes ,the Quickload & Quicktarget are very helpful ,but I've found the load data with some of the slower Aliant Reloder powders to be off by at least 10%, or more. I contacted NECO, and they agreed about the problem, stating it was with inconsistancies in the powder lots. However ,a lot of my R25 and 2 lots of a friends, gives identical results, in three rifles of the same chambering. Go figure. In fact predicted loads on Quickload, using these powders would suggest an impossibility of even getting the correct amount of powder in the cases, which it does, with plenty of room to spare. I haven't used it enough to comment with the other brands of powder, but it was very accurate with Win 748,and a couple of the IMR's that were tried in non magnums. In the book that come with program ,it states to having errors with straight wall case predictability, yet was very close with my .458 Win Mag. and .444 Marlin. Guess no one method is totally reliable, so one needs to use every means at his disposal, to keep his eyebrows intact [Linked Image]

Canon,I have also found Quickload to be somewhat off with RL25 and more accurate with other powders.At the time there was no data available for RL25 nor for the Barnes XLC's that I was trying.Miked the case heads and found the brass was not consistant.Quickload certainly helped finding a good, safe load-much better than flying blind.Frank.

Frank/Hate to hog someone elses post, but just thought I would add, in case your not aware,Neco came out with an upgrade earlier in the year. There is even more powders and bullets included, and the cost is $14.95 +SH The inconsistancies in the Reloder powders have not been changed, but was told they are working on it, and there will be more upgrades to follow. Very nice people to deal with over there. As to the case head expansion thing, I have a lot of confidence in it as it has saved me from getting into trouble, on more than one occasion. Starting book loads turned out to be MAX loads in my guns, but the velocity matched the listed starting loads. Expansion was maximum. One other for instance, manual stated overall case trim lenght. Chamber was .015" shorter. Company's newer edition stated correct case lenght. Mic. readings told me to stop my start loads, and was grateful I was using it. That one could have hurt.

Canon,I'm much obliged to you for taking the time to explain just how to measure for expansion.I have a new box of Rem .338 ultra.I intend to shoot 10 rds. after filing the flat spots as you directed.We have state of the art measuring equipment at my workplace and I'll have them measured and use as a starting point.I have an accurate load with 200 gr bal. tips that's going over 3400 fps using RL 22 with no problems ---- YET!! You can see this is not an academic exercise for me.I've noticed that engineers have a tendency to " fall in love " with a problem rather than solve it,so I appreciate straightforward advice on the " this is how I do it basis".When strain gage data doesn't match expected results,it tends to get " weighted".Same with computer models.Thanks,again.

Gene/ I wasn't aware of your wanting to mic. the Ultra Mag. cases. As per anything read of the Ultra Mags the rim is rebated, so the flat filing isn't required. It is only for standard cases, such as the 30-06 type, where the rim is just a tad larger than the web just in front of the extractor groove. You should get by just fine ,measuring only about 1/16" in front of the groove. Either measure on say the first number of caliber, or a place you will remember, as long as it is the same place each time, as the cases vary in thickness around it's perimeter. If you are going to take loaded rounds to a range than you can also draw a line ,in line with case,using a fine tip felt pen, and write the case measurement, along this line, using this line as a referance point to take the measurements. After cases are fired, the measurments can be taken at range, or at home, as the numbers are on each case it's easy to keep track of. The ink comes off easily with a bit of camp fuel. On belted magnums I measure on the belt. As with anything this becomes easier as you have done more. I'm sure you will consider this a good indicator if you give it a chance. The Speer rep. in the support dept.,suggested that once you have reached .0005" expansion, (that's one half of one thousands) to decrease your load by 6%,as a saftey factor. I think, but this is me, that this is a very generous factor, but you can be the judge. If you reduce the charges so you have no noticable to .00025" expansion,this seems to match factory ammo. Measuring a few factory rounds should be a good guideline as well, but keep in mind that when a company sells loaded ammo, they are only responsible for the first initial firing. Also ,as the cases are reused, they become work hardened, so do not use as an indicator after the third firing, as the expansion will usually be less unless you have an unusually soft lot of brass. Something else I have encountered, is if you happen to have a hot load, and expansion stetches the case over .001", the sucsessive firings will expand more freely. This would indicate to me, that the brass has reached it's yield point. Hope this helps .

Canon,I had brought this up originally in connection with my .257AI and in that instance the filing will be necessary.I thought about the rebated rim after I had posted my last message.The 338 has my attention right now.It wouldn't have occured to me to use the headstamp lettering as a reference.It seems the larger circumference of the ultra may be expected to expand more than an 06 for instance at the same pressure,same hardness of brass,etc.,or am I thinking backward? In other words,does .0006 have the same meaning in either case? Thanks again.

Mr. Howell/I'm not sure if your aware,but your name was mentioned in another post, in regards to your above post discussing the measuring of case head expansion. I think it more appropriate if the discussions were with the source. Hopefully you can answer a couple of my questions to clarify your findings in this proceedure. Let me first say that I am not trying to represent myself or my ideas, as being cast in stone. I am here to learn, and to share ideas, of what can be dangerous ,if not fatal, should things be done incorrectly, or with unsafe proceedures. As to testing pet loads, showing 70-75000# pressure, I can certainly go along with that. I have a couple buddies that did in fact set the headspace back on their rifles, with their pet loads. This probably is not possible with loads within SAAMI guidelines, unless of course one wouldn't remove the sizing lube from cases, which one of them didn't. He would merely wipe it off a bit with a rag. Your relating the blown action story is a case of inadvertantly using the wrong powder, which is unfortunate, and very possible for one to do if thoughts are distracted. However I feel this is giving the case head expansion method a bad wrap, because it's not related. PO Ackley lists several reasons for blowing up actions and barrels, all of which happen through some form of carelessness. One I just heard yesterday is to polish your chamber, which I think a lot of folk do. The statement that leaves a big question mark in my mind though, is the one of no measurable expansion of the brass cases with a pressure of 80,000# psi. I'm not doubting this happened, I only have to question why or how is this possible. As brass is used as the weak link in a firearm, to expand and seal the gasses out of the action, and the shooters face. It has to expand to do it's intended purpose. In my limited testing and experience, measuring case expansion of new factory ammo, Ive yet to fire a round with no measurable expansion. Does this indicate that factory ammo is in excess of 80,000# psi ? I don't think so, so is it possible you tested cases that had several firings, and had become work hardened ? Or as a second thought is it possible the chamber on the test barrel was of tight tolerance, so as not to permit case expansion? Perhaps you could help clarify these questions, as I've only started this measuring practice a couple of years ago and had just become somewhat confident with it. Now ,after your comments about it ,it leaves a certain amount of doubt. I'm sure there are reasonable explanations for everything that happens in a firearm, and hopefully through discussion, nobody gets their nose scorched, or worse. I'm not trying to substitute a mic. for pressure test equipment, but only as a tool to add to the safety of all the other indicators one can use to prevent an accident. If someone approaches handloading too agressively, even with the most sophisticated pressure test equipment, this will only tell him at what pressure his action failed.

Gene/ I have not used different readings for standard or magnum cases. I am only assuming the magnums are loaded to higher pressures, the brass at web is of heavier construction. There is no refference to different measurements in the Speer Load manual, that I noticed. One could confirm this with a Rep. at Speer ,by calling (Pacific time I believe)800-627-3640 If you have over .0015"-.002" case head expansion, you will have loose primer pockets be it standard or magnum cases. If you have loose primer pockets ,there is measurable expansion.[This message has been edited by Canon (edited April 17, 2001).]

Canon, there is not any hard fast rule in what pressures are between mag and standard cartridges. The saami psi listing for the 22-250, 6mm rem, 270 win, and 300 weatherby are all the same - 65000 psi. the 708 rem and 7mm rem mag likewise all list at 61000 psi. The brass at the web "may be" heavier but the larger area of the case head gives the pressure more area to work on. 65000 psi over .473" on a std case is not going to have the same effect as it will over .532" on a mag case.

Seems like we have a good discussion going here.I appreciate that.Joe adressed the point I was wondering about from my oil patch days dealing with pressures in pipe.As diameters go up,wall thickness must increase or pressures must be lowered.From those same days I noticed that engineers were at their best explaining just why something " busted or broke ".That's right in line with Canon's closing comment.I'll try to get some readings for anyone interested enough to look at them.Again, I'm much obliged.

Gene/ I obviously didn't choose my wording right in my last comment.When I stated if you have loose primer pockets, you have measurable expansion. With a six digit mic., you have measurable expansion all the way up to and including that point. The point I was trying to make, was that if you have a dangerous load of 80000#, you should think there would be a loose primer pocket, therefore measurable expansion. Give it a whirl. If you prove me wrong I will apoligize to everyone here, and take the campsite off my favorites list. Over and Out

Canon, I'm not Ken, but I can offer my views:I have a couple buddies that did in fact set the headspace back on their rifles, with their pet loads.Uhhmm, with their pet loads or while using their pet loads? Galling the lugs is easy on almost all actions, especially stainless ones. I've seen lug setback caused by this more times than I care to remember... The only actions I would use without some form of lubrication on the carefully cleaned lugs are old Mauser's and perhaps Sako's.This probably is not possible with loads within SAAMI guidelines, unless of course one wouldn't remove the sizing lube from cases, which one of them didn't. He would merely wipe it off a bit with a rag.Two things: 1) I really think you are exagerating the strength of a few thousandts of brass... Less friction between case and chamber will indeed serve to increase bolt thrust; given that you have a measurable headspace situation; but not at all by a dangerous amount. With a tightly fitted case (zero headspace) the difference would be zero.zero...2) Wiping with a rag is a good way to remove case lube.PO Ackley lists several reasons for blowing up actions and barrels, all of which happen through some form of carelessness. One I just heard yesterday is to polish your chamber, which I think a lot of folk do.Horse hockey. See my last reply. FWIW, Parker Ackley had no piezo electric pressure transducers or the like, he was wildly "guesstamating" pressure.The statement that leaves a big question mark in my mind though, is the one of no measurable expansion of the brass cases with a pressure of 80,000# psi. I'm not doubting this happened, I only have to question why or how is this possible. As brass is used as the weak link in a firearm, to expand and seal the gasses out of the action, and the shooters face. It has to expand to do it's intended purpose.Sometimes you get head expansion, sometimes not - even with identical (pressure wise) loads. Headspace, chamber/case tolerance at the web, brass alloy, heat treating of the case, work hardening, case temperature prior to firing, peak pressure, mean pressure, profile of pressure curve and of course the little goblins that live under your grandma's house are some factors that affect it...As Ken, and others, have tried to point out, it is a very blunt and unreliable method to measure pressure. In one short sentence: You'd be better off without it.That the brass has to seal off the gasses is true, this is what the neck and shoulder sections of the case are supposed to do - that is also why those parts are the only ones you anneal (just as the manufacturer do after heat treating the whole case). Should the base be as soft as the neck on a fresh case, you'd be eating brass and extractors each time you pulled the trigger.In my limited testing and experience, measuring case expansion of new factory ammo, Ive yet to fire a round with no measurable expansion. Does this indicate that factory ammo is in excess of 80,000# psi ? I've measured zero expansion on numerous accounts, even with wild loads (6.5x55 SE, 140 gr Partition, 3080 fps - hot enough?). I've measured a whole hatful of expansion on known low-pressure loads; albeit with a headspace situation. Further, I've had enlarged primer pockets without measurable web expansion. I do not regard case expansion as related to pressure any more than common sense is related to politicians. Or as a second thought is it possible the chamber on the test barrel was of tight tolerance, so as not to permit case expansion?Well, how do you know how tight your chamber is? If you happened to have a tight chamber, would you consider 4000 fps out of a .30-06 with 180 gr pills safe, as long as there were no measurable case expansion? I'm not trying to substitute a mic. for pressure test equipment, but only as a tool to add to the safety of all the other indicators one can use to prevent an accident.About as handy a tool as a monkey wrench, when you really need a screwdriver - in some situations it might actually work, in others you'd just ruin some equipment and bust a knuckle...If someone approaches handloading too agressively, even with the most sophisticated pressure test equipment, this will only tell him at what pressure his action failed.Very true. This, and of course the risk of serious injury or even death to more people than just the shooter, is why we should use those tools that are proven reliable. A chronograph is a very good instrument for judging pressure, a micrometer is not.I'm sure Ken will share his knowledge yet again. Until then, good shooting.-- Mats B. Johansson[This message has been edited by Mats (edited April 18, 2001).]

Canon,I'm not setting out to prove anyone right or wrong.You have proven yourself " right" by answering my questions based on your experience and observations.Since this is a public forum,I expect others to state their views,but it seems a bit strange that :1.I ask a question.2.You answer my question.3.Others argue with your answer.It's easy to figure the motivation of the first and second parties.Hmmmmmmmm!

Gene/ Your on your own to decide if you want to measure your cases. Obviously, there is enough feedback to indicate otherwize, but I will say again I use a chronograph and go slow. The people who sell reloading components and load manuals must be wrong too. Gees, what was I thinking? Case head expansion is not related to pressure. Pressure can blow an action ,but won't set locking lugs back. People can't blow actions due to carelessness, such as shooting with the cleaning rod, or other obstructions in barrel, inadvertantly using the wrong cartridge or powders, cause PO Ackley didn't have Piezo Electric equipment. Rags work fine to remove lube, even if cases still feel oily to the touch. Maybe I'll take a screwdriver to the gremlins under Granny's house, except, she's been dead for forty years, and the new owners might object and throw a monkey wrench into things. Gotta go ,Gene, I think the horse hockey game is about to start. Don't want to miss it or I'd tell ya about the wild velocities I'm getting from old Betsie.

Canon,Would you mind proving me wrong on one single statement I made? Otherwise: Put a sock in it.-- Mats B. Johansson

Hey guys, OK here's the problem. I have a 240 Gibbs. No published data available. No factory ammo to compare against. How do you procceed to determine the upward boundry of Safe Loads?

Mats/ PLEASE, you twisted everything I said so if I have to, heres one. You do not relate case expansion to pressure. What gives you case expansion, ambient temperature ? Ackley gives several reasons for blowning recievers, none that would be prevented with pressure test equipment.You also stated you have loose primer pockets with no measurable expansion.Did you try large rifle primers? Was the pocket hole too large to start? Gene Williams just measured .003" expansion on some cases, and the pockets were still tight.You asked if I was getting 4000 fps. out of an 06, would I consider it safe, because there wasn't any measurable expansion. Are you saying you have done this? Do I really sound that retarded? I could go on about this , but you only asked for one ,so lets give it a rest. As I stated earlier somewhere, the info is there to ignore or utilize at your discretion. If you feel it's worthless, than so be it,ignore. You obviously have tried this method, unsucsessfully, but I don't know what proceedures you followed, or what instrument of measure you used. I have had good sucsess with it, so I will continue, until someone can instruct me in a better way. As stated earlier as well, if I had an Oelher PBL, I would still continue using this method as well. Nuff said (I hope)[This message has been edited by Canon (edited April 19, 2001).]

JN316 /I didn't notice if your earlier posting was answered. I would have liked to see the answer myself. If you can determine a safe starting load(the first shot always scares the stuff out me) then the Case Head Expansion method should do fine.(in conjunction with a chronograph)

RAY,I dont know if your question about the GIBBS was rhetorical - if so,it was a good one -or if you really need data.The real casualty when the ax grinders weigh in on a thread is the valid questions which go un-answered.Many times the very person distorting the thread is the one with enough knowledge to answer the question.As for the gibbs,I believe I saw data for it on SAEED's website.Try accuratereloading.com.I think that's it.

I posted an apology to KEN on the "scorecard" thread,but in fairness,I should post it here too.Ken,I'm sorry for my disparaging remarks.GENE.

Thanks, Gene II!Check your e-mail.

Gene, others, actually I do have a Gibbs and I assure everyone that there was no negative intent to my previous post. Been shooting the 240 Gibbs for more than a few years now. And have what I believe to be safe loads but a little on the high side. They dont blow primers and they dont make loose pockets with just a few loadings. Oehler says the 100 grains are running just over 3400 from a 25 inch tube which is in line with what I think they should be. I've always looked at as many pressure indicators as I can to make judgemental calls on where we're at on the pressure scales. So without an Oehler M43 its an educated guessing game at best. So I posted to see if someone had a better process for pressure determination on Wildcats in leu of instrumentation than I.Now the case expansion measuring method is great for cartridges that dont require extensive forming. Do you guys also recomend it when the case has been formed using the filler method of forming? When I form the cases using the filler I get about an 80% full form. The shoulder has moved forward and now has correct headspace. But the corners have not yet sharpened fully and remain slightly rounded. Then on the first power load the case becomes fully formed. Would the next firing still produce reliable case expansion for measuring?[This message has been edited by Jn316 (edited April 20, 2001).]

Jn316,For curiosity's sake,I checked SAEED's website and I was mistaken,there is nothing posted for the 240 gibbs.I know I saw extensive load data for it somewhere,and I dont visit many sites.Anyhow,I never saw a gibbs so cant help with tour question.I buy new rem 257 roberts brass and use a upper range load of powder behind a 120 gr bullet seated .025 off the lands for fire - forming.I haven't used canon's rather meticulous method yet - but intend to on next batch - but I cant detect any expansion when compared to new brass.I dont have any std roberts loads fired in this rifle before the A.I. chambering was done. That would seem to be what I would need to have a valid basis for comparison,so I guess we are both in the same boat.I just trust my Nosler and Hornady manuals and load one gr. under max.I did have the good fortune to fire a very hot load thru this rifle a couple years ago and had to hammer the bolt open so I look at that as my "proof load". IT was brought about by letting a max load of WIN 760 cook in the chamber on a 100 degree day,so it doesn't tell me how much imr 4350 is safe, but it tells me I have a forgiving GOD and a strong action!

Gene, The Quickload program I have lists the 257 Improved.If you wish to send me info by e-mail regarding case dimensions,which bullet and powder etc. I can run it through the program and send you a printout of pressures with varying charges of a given powder, along with corresponding velocities for those pressures.Should help you determine about where you are.My email is [email protected],Frank.

Frank,I will take you up on your kind offer since my manuals give no data for rl22 with the 100 gr bt in the 257ai 40 degree shoulder.What case dim. do i need to e mail to you?

Gene,data needed is bullet type (brand) and weight,base shape and whether or not moly coated,bullet length, case capacity of water at overflow in grains weight of H20,cartridge length (overall length loaded with bullet you will be using,powder type and barrel length.Can factor in temperature,altitude if you think it will be unusual such as really hot.

Jn316/ I have a .300 Macdonald,which is an improved 300 Win. It also takes two firings to get the case properly formed, with neck turning after the first firing. This method of measuring case head expansion, has worked well for me, as well as the man who designed the cartridge. He has built quite a few rifles in this caliber, as well as three other calibers on this improved cartridge. Most times the people having their rifles rechambered, or rebarreled, will get him to form the brass as well. He has fired countless thousands of rounds, using this method with no mishaps. After all of the discussion of this method being unsafe in the last few days, I referred to my loading log. In the log including the .458 & .375 magnums, on down, the loads I have chosen safe for my rifles, are usually two to five grains powder less than the load book maximums. One example is for two .375 H&H rifles, a Mauser and a Sako, the load I chose to be a safe maximum, using the matching components, same lenght barrel, 270 gn X bullet, is the starting load in the Barnes manual. With two more grains powder, there were no visible signs of pressure, but only an increase of 30 fps and more noticeable recoil.The measured expansion was .00035",(one third of one thou.)so I reduced the powder to start loads. Accuracy was good at this point as well. My point being to all this, is if all my rifles have loadings below book maximum, and I do use the coinsiding manual,to match bullet make, there is measurable expansion, than I would have to think this method is safe. If you use Centurions info, new cases, and these measuring proceedures, you should come up with a load, that you have some confidence in. Hope this helps and good luck. PS. If the first firing does't completely form the case, there is a good chance there is no measurable head expansion. If you confirm this ,than I would say you have a Mulligan.

A most interesting thread this has turned out to be. I for one and I'm sure most have come out with a little better feel for determining pressure signs. And its not just one sign that we should concentrate on. Pressure can show in any number of indicators. So we must watch for all of them.Gene, the Gibbs cases may be formed from just about any 06 based case. IE: 30/06, 270, 280, 25/06 etc. The trick is to maintain a tight headspace on the first forming load because the Gibbs has about .10 inch longer headspace than the 06's. I start with necking down to produce a false shoulder thats really tight when chambered. If its not, I get too much stretch in the case just ahead of the web area and the case will separate in about 3-4 loading. When fired with some pistol powder and corn meal the shoulder is pulled forward and good headspace is produced. Although the shoulders do not yet have sharp corners. The next firing with a medium loading of 4831 and a 100 gr bullet fills everything out nicely. This case is now ready for testing. Hopefully the case has not been work hardened so much that it wouldnt be a reliable one for measuring case expansion.Cannon, good to hear someone has been down the same thought processes as I. Your 300 widcat sounds very interesting. With a little luck I'll find some range time and test the case expansion thing with rounds that start approaching what I already know is very hot.....Ray[This message has been edited by Jn316 (edited April 22, 2001).]

Cannon,If you file down the rim on standard cartridges to get the base readings, how do you account for the slightly out of round chamber? I mean if you chamber and fire a round then measure the base on the filed section or align the mic with the headstamp, how can you be sure that you aren't measuring the smallest expansion due to the tighter/stronger part of the chamber?Wouldn't that create a problem of false readings unless the case is in exactly the same position every time you fired it?Also I am curious about the comment in the Speer manual on p.55 "New cases can give deceptive readings. The first firing of any case will usually cause more deflection of the brass than subsequent firings. At Speer, we start with once-fired brass so the initial deflection is already accomplished"If I were to measure factory rounds, how do I compensate for the greater initial deflection of the cases? Doesn't this cause a false pressure reading right from the start because the expansion is based on brand new cases with greater deflection?Speer also states that .ooo3 to .ooo5 expansion is generally accepted as representing pressures in the 5o,ooo C.U.P. range. How much pressure does it take to expand the case .ooo1, .ooo2, .ooo3 etc?Turok------------------ Make it idiot proof, and some one will make a better idiot

The more I look at this the more it seems it more accuratly be called "the case retraction method of estimating pressures".The idea that the brass always expands to the chamber wall and that pressures exceeding the elastic limit of the brass dont allow it to retract,thus resulting in permanent expansion,makes the speer statement make sense to me.I'm probably too dumb to be confused!

Turok I'm not sure I understand the first part of your questioning, but I will make an attempt to answer what I think you are asking. The need to file the rim on standard cases, is to allow the use of a standard mic.(blade micrometer would work without filing, but is the equivelant cost of a new rifle. I see you are from Canada, so the cost of a Starrett digital mic. in six digits is $800.00 plus tax. Standard is $200.00 + tax in Canadian dollars from the House of Tools) The part measured, is the thick portion of web, just in front of extractor groove. This portion of web(I believe .200-.220") does not enter the chamber. If you feel that filing a very slight amount of the rim (as rim is slightly larger, usually, than the web)would somehow effect the measurements, than you could take the correct amount off, all the way around, by utilizing a lathe or perhaps a drill press and a file. Personally, I don't feel this to be necsessary. Turok, without meaning any disrespect, and the fact that I do not have access to pressure test equipment, I would suggest you give a call to the fine people at Speer. The number was posted earlier, and it is toll free number. They can perhaps clear up any or all questions you have. I did get the numbers you seek from a friend but of course, since this is second hand info that cannot be verified, I would preffer you get it directly from the source. In addition, my wife has a leg long list of spring season things to do. This, I have to take care of before I can apply some of this info to developing ammo for a new rifle, just built. As the bear season is upon us,I'm struggling to prepare. Thanks for your understanding. Canon

Cannon,Please don't worry about offending me, I understand peoples limitations and the fact that these boards do not easily lend themselves to the 'tone' of a persons voice.I would like to state that I am familiar with the proceedure of case head expansion. I have read a fair amount about it on the various boards, in the Speer, Nosler and Nick Harvey manuals as well as in Ken Waters Pet Loads. Like yourself, I have used it for a few years now. Although I do not rely on it, I use it out of sheer curiousity and as a means to collect data for when I am able to purchase strain guages. I have found a cheaper setup that runs for under $3oo US. This is enough equipment to use on three guns. Obviously the less guns you use it on the cheaper it's going to be.Anywho, what I was attepting to ask had nothing to do with the integrity of the case after the rim was filed, or the interference of the rim before firing. What I was asking is more related to the idea of no chamber being perfectly round and that there are weaker points in the barrel steel that would allow for more expansion in certain spots of the case head.Now if you measure only one spot on the case via filed rim, it would imply that all the cases were positioned in the chamber in exactly the same way every time. If it is not, wouldn't you get different readings (+/-) with the cartridges due entirely to the variations in chamber rather than those in the pressure? If this is the case then wouldn't that essentually throw off the accuracy of the whole process?Turok------------------ Make it idiot proof, and some one will make a better idiot

Turok Now that you have broken it down finer, I finally get it. This is a good point. Up until now, I was going on the assumption that my chambers were in fact round. One more variable to the long list. Some target shooters do in fact place their rounds in chambers, in the same position to make everything as consistant as possible from shot to shot. If one uses a referance line on the cartridge anyway, it would of course make it easy to position it in the chamber to eliminate this one variable. My old friend, who did advise me of the measurement method ,did not make referance to this point.It was discussed on the topic of benchrest shooting. I will confer with him about it, to get his views. Up to this point, with the rifles used, any readings I have taken, have corresponded to the increase or decrease of powder used.With the exception of some readings taking a large increase, with only a small amount of powder being added. This of course is where I would determine where I wanted to stay with my load for this round. I would agree if the chamber was in fact out of round, this could help increase(decrease) the measurement,and your suggestion of placing the cartridge in the chamber at the same position each time, is a good one. If this variable does in fact exist in my rifles, I would suggest it is of small enough significance to not have affected any of the loads, I haved deemed safe in my rifles. I also suggest relying on an average of readings from several firings, rather than a limited few. One day soon, I'm going to have to give my lady the bad news, and tell her the new Oehler 43 is on it's way. It is after all in the name of safety, right? Surviving this, a bore scope should be easy. [Linked Image]

Sorry, guys, I meant to answer some of your questions long before now but got too busy stomping snakes in other places. Got pretty tired doing it, too!One confusion that I meant to clear-up earlier is this one:"I'm still trying to figure out your post,KEN,about a blown up rifle due to incorrect powder charge when the discussion was about case head measuring.Do you think we dont know rifles will blow up?"I was sure I'd had a good reason to cite this pile of gun chunks and slivers in this thread but had to go back to see exactly what was the immediate context of my reference to it. I was sure that the context should've made it clear why I mentioned it. It seems clear enough to me, of course, but here it is for your second look:"Cases already too hard to show 'excessive' expansion here (some, even at 80,000 lb/sq in.) are especially likely to become brittle in repeated firings and reloadings, and spew wild gas and bits of brass into a shooter's face. I have on hand now a rifle utterly demolished when half the head of the case blew back through the action. The rest of the case is still in the apparently unharmed barrel, but the receiver is in many pieces, and my friend still has one piece of brass in his face (a larger chunk was surgically removed)."My point in that earlier post was that cases can (and do) burst and wreak a good bit of damage without bursting or swelling the barrel � that they can (and do) "spew wild gas and bits of brass into a shooter's face."As an example of what wild gas can do, without bursting or swelling the barrel, I mentioned that "I have on hand now a rifle utterly demolished when half the head of the case blew back through the action. The rest of the case is still in the apparently unharmed barrel, but the receiver is in many pieces, and my friend still has one piece of brass in his face...."Hope the point is clear now, and that you can see the justification for citing this once-was-a-rifle in this thread. It fits. If it's still not clear to you WHY it fits, please read that paragraph again until it's clear to you. I don't know how to make it any clearer. (Or I would.)Shalom!

Well I just measured a number of cases and have taken both the largest and the smallest diameter. The cases measured here were fired in a semi-custom .338-o6AI on a Rem7oo with a Douglas premium barrel. The numbers are as follows:Largest----- Smallest.4673 ------ .4671 .4673 ------ .4670 .4674 ------ .4671 .4674 ------ .4672 .4673 ------ .4671 .4672 ------ .4671 .4674 ------ .4672 -------------------- -------Average------ .4673 ------ .4671I would like to point out that the method I used is in strict accordance to the method Ken Waters uses, which is the measuring of web expansion and not base expansion. Notice the variations between the two. In at least one case there is a difference of .ooo3 and on average there is a .ooo2 difference.Rather than assuming that the chamber is round, I suggest spinning cases as you measure to get the most consistant readings and reconsider the measuring of just one section. And as I'm sure everyone knows, each chamber is different. Like anything else with handloading, rifle chambers are going to vari. Don't assume the amount, know.In any event, I still wonder how the greater initial deflection of the new cases is going to affect the readings when we try to compair the numbers obtained from factory ammo to the once fired cases.Turok------------------ Make it idiot proof, and some one will make a better idiot

I just thought of this after I posted the last one. Why does this meathod of expansion measuring allow additional expansion over the factory load, when the people at the factories with testing equiptment have determined the safe pressures, which is an unknown amount to those without pressure equipment?Wouldn't this meathod of be safer/better off by equalling factory expansion rather than exceeding it?Turok------------------ Make it idiot proof, and some one will make a better idiot

Some very good points are being raised in response to my original question;How do you do it? Here are some points I[ FWIW ] keep in mind:1.One cannot prove a negative.Therefore,one man may prove to his own satisfaction that the method-however he interprets the mic readings-has merit.Noone can prove it is without merit.2.Strain-gaging is not without it's detractors.3.The people gathering data for publishing reloading manuals arrive at different conclusions using the same [ in some intances ]methods of measuring for chamber pressures.4.Anyone interested enough to moniter his cases is not the sort of guy who is likely to blow himself up by using too much of the right powder.5.A modern rifle action is PROBABLY--I said probably--not going to destruct at even 20 percent over maximum design pressures.I say this not because I have inside information,but because the practice of using proof loads would not have had any value unless they were in that range at least.Just the wanderings of an idle mind.

I give up. There's too much specious* "reasoning" here for me. I've shot all these points down, repeatedly, for months and years, and so have others, and they just keep cropping up and attracting ardent followers. The support is flawed and easily disproved, but you fellows are just too many for me. I'm simply worn out from trying to warn of the dangers that I fervently hope NEVER befall you. Others have already concluded that measuring web expansion is a weed idea that can't be killed, and I've finally reached that conclusion too.Come to your own conclusions, mike cases to your hearts' content, and pray that you're as safe as you've convinced yourself that you are.Shalom!* "spe�cious (sp��sh�s) adj. 1. Having the ring of truth or plausibility but actually fallacious: 'a specious argument.' 2. Deceptively attractive." [American Heritage Dictionary]

Ken Howell,I have read and understood (well most of them anyway - that math part from another thread still gets me [Linked Image]

) your posts here and throughout the many threads that this topic has spawned, and I must say I agree with you. I really wonder what the actual pressures are running at when such things as variances in case hardness, out of round chambers, steel strength, initial deflection, and human error in measuring are taken into account.As I mentioned before, I am hoping to obtain strain guages in the near future. And while they do have their problems, the pressures obtained by measuring a consistant factor, like you have pointed out, should produce closer results than the measuring of an ever changing factor such as the case.Turok------------------ Make it idiot proof, and some one will make a better idiot

Turok / I would suggest that your measuring the fired cases has told you that your cases are out of round, and not necessarily the chamber.This would be a very good reason to measure your expansion at one point exactly, and onlyYou are assuming that your chamber is out of round, because the fired cases are. I just measured some Federal Premium .458 mag ammo, cause that was the first box I came across, with both fired and unfired rounds.They were measured according to a Speer rep. just in front of the belt, even though this is contrary to what I've been told in the past. Normally I measure on the belt on magnums, I did it this way to match the method you used.UNFIRED LOADED .458 FACTORY ROUNDS Largest Smallest deflection .51130 .50945 .00185 .50980 .50860 .00120 .51125 .50845 .00280 .51110 .50960 .00150 .51095 .50865 .00230Average deflection .00193Fired brass from same box Fed..458.51345 .51260 .00085 .51320 .51265 .00055 .51385 .51310 .00075 .51405 .51350 .00055 .51320 .51250 .00070Average deflection .00068 The average deflection is .00125 less after the cases were fired. This ironed out some of the wrinkles, but does it still mean my chamber is out of round? Or will this number decrease with progressive firing?I would think a chamber casting be a more accurate method of checking the chamber for inconsistansies. [This message has been edited by Canon (edited April 25, 2001).]

Turok / In answer to your post, and I hope this is my last post on this topic. The measurement method I described does not allow for more expansion than factory expansion.In fact it is quite a bit less ,if the guidelines are followed. The factory .458 loads, measured on the belt were .0009". Just less than one thou. Speer suggested loads, going up to .0005", then reducing by 6%. A very generous saftey factor. WELL below published maximums. (Which is what Ken suggested days ago) [Linked Image]

I built a load ,worked up with an Oehler 43 PBL, by a Stan Skinner of Guns & Ammo, Feb.2000. He gives a list of loads ,that are a couple of grains under published loads, and the expansion with new cases are .0001" The expansion on subsequent firings should be nonexistant. It has an allowance built in for an unseasonaly warm hunt or climate.If a person does need more velocity or more power, rather than load a round to the maximum pressures, go to a larger cartridge. [This message has been edited by Canon (edited April 25, 2001).][This message has been edited by Canon (edited April 25, 2001).]

Working on the theory that no case is really round, and using the Ken Waters method of pressure ring measurement, I've been using my run out comparator, and working with the average expansion. I'm not exceeding the factory ammo expansion, but can understand how using factory ammo in an improved chamber could give you less expansion than the SAAMI pressure limits. I know I'm not using the very finest equipment available but am content that I can judge within a half a thousandth. As Waters stated his method helps you "judge" not "measure" chamber pressures.As for the destroyed rifle, Ken Howell referred to, once the gas gets out of the case and into the action, destruction is nearly a certainty. I think Remington's theory of confining gas escaping from the case to the chamber area is the best solution. The Remington bolt face will obturate sealing the gas in the barrel, and preventing the damage other actions can experience. Of course you can't use the rifle again, but it beats not haveing the use of your head, hands or other parts of your body.[This message has been edited by Slamfire (edited April 29, 2001).]

Please explain obdurate.I shoot remingtons.

The steel ring at the head of the bolt that surrounds the cartridge, expands outward, sealing the chamber from the rest of the action.

This has been an interesting thread, but I am more than a little curious as to how Remington manages to obturate the firing pin hole in the bolt face.

In a "subject" Model 700 .30-06 that I examined for an insurance company, the bolt's "solid ring of steel" around the head of the case broke around that much thinner ring of steel around the extractor. The steel there is just a bit thick for rolling a cigarette but rather thin for anything else (except maybe an X-Acto blade).Debris flew and wild gas flowed. The shooter had a piece of metal removed from his eye. I didn't see it. The doctor had apparently discarded it. I didn't see any evidence of any obturation. Anywhere.Another good theory blown to Hell.

Y'all all know that i dont know enough to want to argue about this so tell me what action is better than the rem as for as destructing in a manner that offers less danger to the shooter?The equivalent of crashworthiness in an airplane or car i guess is what im asking.

<BLOCKQUOTE>quote:<HR>Originally posted by Ken Howell: <snip>Another good theory blown to Hell.<HR></BLOCKQUOTE>Hey Ken, you aren't supposed to be reading this thread any longer. Us specious speculators were supposed to be able to run wild and free without any regard for facts or the scientific method ;-)As for actions that behave best, when Really Bad Things Happen (tm)? I believe the best action would be the one belonging to the guy next to you, rather than yours... A lot of folks swear by the 98 pattern Mauser though.On a serious note, Ken, have you ever heard of or seen an action that had failed catostrophically? something on the order of all the locking lugs failing, or the locking shoulders in the action shearing? Thus sending the bolt speeding backwards much faster than you really wanted?Regards, Scott

Gene -- As far as modern bolt actions are concerned, if one has a clear superiority over another I have not seen it conclusively demonstrated.The current "pre-64" Winchester M70 handles escaping gas a little better than the real pre-64 by putting a gas baffle behind one of the locking lugs.The Remington M700 vents the gas out the receiver ring. (That's what that little hole in the receiver ring is for.)The Browning and Savage have essentially the same lock up as the M700, although the Browning uses three lugs instead of two.The Ruger directs escaping gas down into the magazine well.I guess that probably the Weatherby Mark V action will handle escaping gas as well as any and better than most.If any of these designs are inherently stronger than the other, I haven't seen that conclusively demonstrated either. Still, a bolt that locks with lugs that are milled from the steel bar rather than brazed on would seem to me to be inherently stronger.On the other hand, I have never heard of, much less seen, a Mauser-type bolt action that failed completely.As an example, a gunsmith buddy of mine who lives in Michigan specializes is converting Mauser 98s into modern sporting rifles. One of the conversions he did was to a 270 Winchester. This particular rifle was inadvertantly dragged through some slush during an elk hunt, and the stuff froze solid in the barrel. When the hunter pulled the trigger nothing much happened that he was aware of, but the bolt was essentially welded shut. My gunsmith friend couldn't get the bolt opened either and had to remove the barrel. Ever seen a belted 270 Winchester case with a head diameter the size of the bolt face? A primer pocket so expanded that you could stick your little finger in it?

Yes, Scott, I have. It shed its lugs and handle, and the bolt body went into the shooter's face, from his eye socket down through his upper and lower jaws, broke his collar bone, and lodged inside the base of his neck.All you have to do, to see the same thing, is to do what he did, as long as he did. I wouldn't, if I were you. But you're on your own. �o)I also have here some of the pieces of a friend's once-nice custom FN Mauser that failed catastrophically when half the head of the case blew away under extremely high pressure and the escaping wild gas blew the receiver and stock to bits. My friend still has a piece of brass inside his face after having a larger piece surgically removed.[This message has been edited by Ken Howell (edited April 30, 2001).]

Well actually, OK Shooter, they don't obturate the firing pin hole. They just let the spring stack up. Not enough gas get out to damage the interior of the action. And the 788 had a smaller hole to start with.

OK SHOOTER,much obliged for the answer.

I now stand corrected. Now I have heard of a Mauser-type bolt failing completely thanks to Dr. Howell. [Linked Image]

Ken, if I can find the time to make it back up to your part of the woods, I would like to see those pieces. Life has been entirely too peaceful lately, and I really do need something to induce nightmares. [Linked Image]

OK SHOOTER,I dont have a recipie for inducing nightmares that doesnt include at least two ex-wives,and if you have the ingredients,you dont need the recipie!I do have an idea which can disturb the peace:Go to one of these boards and post a "how do you etc. etc." The eruption which often results is - using my place as an illustration - akin to a chicken snake getting in the chicken house.THere's a lot of cackling going on which is confined to tiny minority of the critters around here and goes entirely un-noticed by the rest.GRIN.