Home Forums Reloading Big Game Rifles 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.<p>[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.<P>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.<P>� Many cases don't expand enough, even at 80,000 lb/sq in., to warn of risky or excessive pressures.<P>� 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."<P>� 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).<P>� 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.<P>� 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."<P>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.<P>Some carefully lab-tested loads, developed by miking case rims, webs, and expansion rings, have developed 80,000 lb/sq in. without measurable expansion.<P>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.<P>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?<P>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 !!]<BR> 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?<BR> So far this represents about 15 min. typing for me so if I remember what I was going to ask it's a miracle.<BR> 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?"<P>No � it's just the most reliable field method economical enough and practical enough to be available to us ol' boneheads out here. �o)<BR>

Dr. Howell,<P>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?"<P>� .220 Howell<P>� FN Mauser action<P>� 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 other<P>That 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.<P>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.<P>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.<P>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.<p>[This message has been edited by Ken Howell (edited April 14, 2001).]

Gene/ On standard cases, without the use of a<BR>blade micrometer, it helps to file two flats<BR>opposite each other on the rim. This allows you to measure the web ,just in front of the<BR>extraction groove. A small 6" file works fine<BR>as only one or two thou.,have to be removed.<BR>On magnum cases, measuring on the belt, at the exact spot each time ,works fine. Rimmed cases require a blade mic.<BR>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.<BR>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.<BR>It has been my experience that measuring case head expansion ,combined with a chrono-<BR>graph, that maximum loads are achieved ,long<BR>before any pressure signs are visible to the naked eye. No ejector marks, stiff bolt lift<BR>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. <BR>I would also like to add that I am not stating that any reloading method to be safe.<BR>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<BR>One more example ,is even with proper pressure testing equipment, proving the load<BR>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<BR>very helpful ,but I've found the load data<BR>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<BR>in the powder lots. However ,a lot of my R25<BR>and 2 lots of a friends, gives identical<BR>results, in three rifles of the same chambering. Go figure. In fact predicted loads on Quickload, using these powders would<BR>suggest an impossibility of even getting the<BR>correct amount of powder in the cases, which<BR>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 <BR>book that come with program ,it states to having errors with straight wall case predictability, yet was very close with my<BR>.458 Win Mag. and .444 Marlin. Guess no one<BR>method is totally reliable, so one needs to<BR>use every means at his disposal, to keep his<BR>eyebrows intact

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<BR>bullets included, and the cost is $14.95 +SH<BR>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<BR>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<BR>book loads turned out to be MAX loads in my<BR>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.<BR>Company's newer edition stated correct case<BR>lenght. Mic. readings told me to stop my start loads, and was grateful I was using it.<BR>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.<P>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".<P>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.<BR>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,<BR>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<BR>good indicator if you give it a chance. The Speer rep. in the support dept.,suggested that once you have reached .0005" expansion,<BR>(that's one half of one thousands) to decrease your load by 6%,as a saftey factor.<BR>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<BR>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",<BR>the sucsessive firings will expand more freely. This would indicate to me, that the brass has reached it's yield point. Hope this helps .