Home Forums Reloading Big Game Rifles Measuring case head expansion

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<BR>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.<BR>As to testing pet loads, showing 70-75000# pressure, I can certainly go along with that.<BR>I have a couple buddies that did in fact set<BR>the headspace back on their rifles, with their pet loads. This probably is not possible with loads within SAAMI guidelines, <BR>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.<BR>Your relating the blown action story is a case of inadvertantly using the wrong powder,<BR>which is unfortunate, and very possible for one to do if thoughts are distracted. However<BR>I feel this is giving the case head expansion method a bad wrap, because it's not<BR>related. PO Ackley lists several reasons for<BR>blowing up actions and barrels, all of which <BR>happen through some form of carelessness. One<BR>I just heard yesterday is to polish your chamber, which I think a lot of folk do.<BR>The statement that leaves a big question mark<BR>in my mind though, is the one of no measurable expansion of the brass cases with<BR>a pressure of 80,000# psi. I'm not doubting this happened, I only have to question why or<BR>how is this possible. As brass is used as the<BR>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<BR>measurable expansion. Does this indicate that<BR>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<BR>is it possible the chamber on the test barrel<BR>was of tight tolerance, so as not to permit case expansion? Perhaps you could help clarify these questions, as I've only started<BR>this measuring practice a couple of years ago<BR>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<BR>If you have over .0015"-.002" case head expansion, you will have loose primer pockets<BR>be it standard or magnum cases. If you have <BR>loose primer pockets ,there is measurable<BR>expansion.<p>[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.<P>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<BR>to everyone here, and take the campsite off my favorites list. Over and Out

Canon, <P>I'm not Ken, but I can offer my views:<P><B>I have a couple buddies that did in fact set the headspace back on their rifles, with their pet loads.</B><P>Uhhmm, <I>with</I> their pet loads or <I>while using</I> 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.<P><B>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.</B><P>Two things:<BR>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...<P>2) Wiping with a rag is a good way to remove case lube.<P><B>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.</B><P>Horse hockey. See my last reply. FWIW, Parker Ackley had no piezo electric pressure transducers or the like, he was wildly "guesstamating" pressure.<P><B>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.</B><P>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...<P>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.<P>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.<P><B>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 ? </B><P>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. <P><B>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?</B><P>Well, how do you know how tight <I>your</I> 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? <P><B>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.</B><P>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...<P><B>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.</B><P>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.<P>I'm sure Ken will share his knowledge yet again. Until then, good shooting.<P>-- Mats B. Johansson<p>[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 :<P>1.I ask a question.<P>2.You answer my question.<P>3.Others argue with your answer.<P>It's easy to figure the motivation of the first and second parties.<P>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<BR>locking lugs back. People can't blow actions<BR>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,<P>Would you mind proving me wrong on one single statement I made? Otherwise: Put a sock in it.<P>-- 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.<BR> <BR>You do not relate case expansion to pressure.<BR>What gives you case expansion, ambient temperature ? <P>Ackley gives several reasons for blowning recievers, none that would be prevented with<BR>pressure test equipment.<P>You also stated you have loose primer pockets with no measurable expansion.<P>Did you try large rifle primers? Was the pocket hole too large to start? Gene Williams<BR>just measured .003" expansion on some cases,<BR>and the pockets were still tight.<P>You asked if I was getting 4000 fps. out of an 06, would I consider it safe, because there wasn't any measurable expansion. <P>Are you saying you have done this? Do I really sound that retarded?<BR> <BR>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<BR>you feel it's worthless, than so be it,ignore. You obviously have tried this method, unsucsessfully, but I don't know what<BR>proceedures you followed, or what instrument<BR>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<BR>earlier as well, if I had an Oelher PBL, I would still continue using this method as well.<BR>Nuff said (I hope)<p>[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.<P>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.<P>Ken,I'm sorry for my disparaging remarks.GENE.

Thanks, Gene II!<P>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.<P>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?<p>[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.<P>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.<P>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.<P>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,<BR>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 cornellmontrose.net.Regards,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?