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Posted: 9/17/2012 7:46:07 AM EDT
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I reload for my 556 and shoot them from an a r15.
Was out last weekend and had 2 LC cases separate about 1/2 inch above the base. Got the front 1/2 of the case out of the chamber by shoving in a 30 cal brush from the chamber end, and pulling them out. I check my cases with a case gauge, and they were in spec. Does this mean my chamber is out of spec...too much headspace? Thanks |
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Tell us the loads you've been shooting and the number of times the cases have been loaded.
Your sizing practice using a drop in gage means the cases have as much headspace as you'll ever want. My Wilson gage and the two Lyman gages I've handled cause the sizer to be set up to produce 0.008 inches of cartridge headspace. If your gun is getting worn out, it could add enough to cause failures, but that wouldn't be the first place to look, we need more information about the loads you're using. |
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Quoted:
I reload for my 556 and shoot them from an a r15. Thanks ????? translation please. Do you mean that you are attempting to load to 5.56mm NATO levels? If so, do you know if your rifle(s) have a chamber cut for 5.56mm NATO, .223 Remington, or the intermediate Wylde chamber? Where did you obtain the brass? Was the brass previously fired through a SAW/ squad automatic rifle ? (if you do not know, you might want to ask next time). I believe folks would like to help you, but we need accurate, complete information first. |
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Quoted:
I reload for my 556 and shoot them from an a r15. Was out last weekend and had 2 LC cases separate about 1/2 inch above the base. Got the front 1/2 of the case out of the chamber by shoving in a 30 cal brush from the chamber end, and pulling them out. I check my cases with a case gauge, and they were in spec. Does this mean my chamber is out of spec...too much headspace? Thanks Sir, in my experience due to multiple reloading of cases the wall thickness is diminished near the base of the case in the vicinity of the case web where the wall thickness becomes uniform toward the mouth of the case. Since the case wall extrudes toward the mouth of the case during firing the neck needs to be trimmed to remain less than the max case length. This extrusion contributes to the reduction of the case wall thickness and cannot normally be noticeable from the exterior. The common inspection method is to use a bent paper clip inside the case body and try to feel the "valley" that results from the thinned case wall. You should discard any cases you find that have such a "valley" simply because case head seperations can be dangerous beside being a pain to recover from. For military cartridges a broken case extractor is available to remove the portion of the case that remains inside the chamber. I know of no other sources for other cartridges types for broken case extractors but I assume such tools exist. HTH, 7zero1. |
A case gage is not the best tool for measuring the sized brass. My Colt needed brass to be above the high step on the cartridge gage.. Photo Album 
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I'm still learning something new everyday.
Trouble is I have several ar15s to load for. I'm sure none of them have the same head space. The cases were previously fired several times; Load was 25 gr 2230 with a 55 FMJ oal 2.240 only 2 cases out of 700 fired separated. I did see several that were "stretched" in the same area, but didn't stay in the chamber. I don't think the cases were from a SAW. I have a Wilson and a Lyman case gauge. I use the Lyman as it seems just a little tighter tolerances. The chambers were Colt factory spec. |
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"Fired several times" is your main problem.
I can't check right now and haven't loaded 2230 for a while, but I'm guessing your load is warm, too. Then, you're sizing cases to a generic length. The last two conspire to stretch your brass, and repeating the cycle several times thins the brass to a point where it fails. If you can see an obvious line on the cases about mid body, you ought to consider tossing them, they're done. |
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Quoted:
"Fired several times" is your main problem. I can't check right now and haven't loaded 2230 for a while, but I'm guessing your load is warm, too. Then, you're sizing cases to a generic length. The last two conspire to stretch your brass, and repeating the cycle several times thins the brass to a point where it fails. If you can see an obvious line on the cases about mid body, you ought to consider tossing them, they're done. This is what I was thinking as well Thanks all for the input |
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I can't check right now and haven't loaded 2230 for a while, but I'm guessing your load is warm, too. . . . 25 grns seems to be the NEW max load for this powder, and the 25 grn load apparently performs close to Fed XM193 NATO factory loads. Archives also yeilded this caution by another member: "2230 is one of those powders you need to be real careful about where you get your data and how old it is. Some of the published data is nuts. Lyman 47 list loads well above 27 grains, I maxed out at 25gr and ,y final load was less than that. Makes you glad you worked that load up when things like that happen. Also, be careful about mixing or confusing data from 2230 and 2230C and be careful about getting data from those that may have. They are not the same. Link to thread in archives: http://archery.ar15.com/archive/topic.html?b=6&f=42&t=253253 I do not understand the desire of so many AR owners to try to duplicate 556 NATO loadings; it seems needlessly hard on the gun, has a much thinner margin of error for the home reloader, and apparently it can be hard on brass as well. YMMV. |
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Are you a bolt shooter?
Every case I had seperated was about 1/2 in above the web on a AR. Now an M1A and M1 is different, they seperate at the web as you describe. Quoted:
[ Sir, in my experience due to multiple reloading of cases the wall thickness is diminished near the base of the case in the vicinity of the case web where the wall thickness becomes uniform toward the mouth of the case. Since the case wall extrudes toward the mouth of the case during firing the neck needs to be trimmed to remain less than the max case length. This extrusion contributes to the reduction of the case wall thickness and cannot normally be noticeable from the exterior. The common inspection method is to use a bent paper clip inside the case body and try to feel the "valley" that results from the thinned case wall. You should discard any cases you find that have such a "valley" simply because case head seperations can be dangerous beside being a pain to recover from. For military cartridges a broken case extractor is available to remove the portion of the case that remains inside the chamber. I know of no other sources for other cartridges types for broken case extractors but I assume such tools exist. HTH, 7zero1. |
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Quoted:
Are you a bolt shooter? Every case I had seperated was about 1/2 in above the web on a AR. Now an M1A and M1 is different, they seperate at the web as you describe. Quoted:
[ Sir, in my experience due to multiple reloading of cases the wall thickness is diminished near the base of the case in the vicinity of the case web where the wall thickness becomes uniform toward the mouth of the case. Since the case wall extrudes toward the mouth of the case during firing the neck needs to be trimmed to remain less than the max case length. This extrusion contributes to the reduction of the case wall thickness and cannot normally be noticeable from the exterior. The common inspection method is to use a bent paper clip inside the case body and try to feel the "valley" that results from the thinned case wall. You should discard any cases you find that have such a "valley" simply because case head seperations can be dangerous beside being a pain to recover from. For military cartridges a broken case extractor is available to remove the portion of the case that remains inside the chamber. I know of no other sources for other cartridges types for broken case extractors but I assume such tools exist. HTH, 7zero1. Sir, yes I shoot bolt guns too, but I've never had a case head separation in one. Actually, I've never had a case head separation occur in one of my ARs either. Apparently I learned from my experience with M1As and M1s and discovered how to inspect cases as I've described to avoid similar problems with the ARs. Generally speaking since the loads I use in my ARs are fairly hot the primer pockets become loose before the incidence of sufficient thinning of the case walls can occur and I recycle the brass. The point I was trying to make for the OP was that case head separations occur due to repeated extrusion and trimming that results in diminished case wall thickness somewhere along the interior circumference of the case. It doesn't really have anything to do with head space dimensions or the exterior dimensions of a resized case. JMHO, 7zero1. |
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It doesn't really have anything to do with head space dimensions or the exterior dimensions of a resized case. JMHO, 7zero1.
A separation is possible in the web area or in the body of the brass. It is caused by to much head clearence, from pushing the brass shoulder back to far on full length sizing. Another cause is excessive headspace in the rifle, set at the time of manufacture. Normal slop would be around .005" When head clearence gets over .010" the case may separate. This may take a few firings. Old military riflles with excessive headspace will have case head separations on the very first firing of factory ammo. Keep in mind that factory ammo may produce the most slop/head clearance, as it has to fit all chambers. Photos 
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I had some case-head separations when I first started loading for the AR when I began shooting high power. They occurred after only 2-3 firings. Most HP shooters size their brass by pushing the shoulder back only 0.002". That assures that the round will fit in rapid fire and does not work the brass too much. The case gauge didn't show how much the shoulder was being pushed back, which I assume was too much.
I purchased an RCBS Precision Mic, which can measure the fired case from the base to mid shoulder, roughly the chamber size. I can set my sizing die, size a case, and measure it to see if the shoulder has been set back 0.002". Adjust if necessary. Since then I've not had any problems. A Sinclair or Hornady tool will work as well, but calipers are needed for those. Different rifles may have different chamber sizes, so I sort my brass by headstamp. The LC03 goes in my service rifle, e.g., Remington in the LaRue upper, etc. YMMV. |
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