I just finished loading up 1K of '07 and '08 LC headstamp 5.56mm. The brass had the crimp removed on a Scharch machine, but no other sizing or prep done.
500 rounds of Hornady 75 gr OTMs over 23.5 gr of Varget, 2.26" OAL.
500 rounds of Hornady bulk 55 gr FMJ over 24.5 of X-Terminator, 2.255" OAL.
Fired a few ladders of the Varget load starting with 22.5, to settle on 23.5 in the new rifle. 23.9 (Sierra max AR load) showed mild pressure signs, none with 23.5 gr with good accuracy, so I loaded up the rest on my Autocharge (all weighed to be spot-on).
First 100 rounds of the 23.5 gr load through the rifle (plus the 80 in the ladder) with no issues.
Next 100 rounds of that 23.5 gr load I had two case failures within the first five rounds. I didn’t notice the first one until after I policed up the brass. The shoulder of the second round stuck in the throat and jammed the next round chambered.
These were not split necks or cracks, but major failures. Fortunately, no damage to me or the rifle (my thanks to BCM and thier suppliers). Both rounds of brass were split into three pieces with horizontal splits that ran the circumference of the case (looked much like a case head separation, but further up the case and a second identical failure up closer to the shoulder). The primer had flowed a bit on those two cases, but nothing major that would’ve indicated a highly overpressure round.
What could be causing these failures? I pulled the bullets and re-weighed the charges on the lot with the failures and they were all spot-on +/- .1 grains.
Is this a symptom of SAW fired brass, or do I have a bad lot? I’ve loaded up thousands of LC once fired cases (usually at least 5 times), and they’re usually very good in terms of longevity. I’ve never experienced any failure modes like this before, and certainly not on the first reload.
How did you size the brass? If its once fired I always full length size it in small base dies so you know where you are starting from. If you did the first shots than neck sizing only is probably ok.
I believe as Rumplstlskn said that the brass or at least some of it was fired in SAW’s,the chambers are somewhat oversize,due to the conditions that machine guns are fired under.
I FL sized these in a Hornady CGND die. It is not a small base die, but does size them down slightly smaller than my Redding and Forster dies.
I do not know if these were fired in a SAW or not for certain. I purchased them from TJ Convera’s online, but he makes no statements as to if they’re fired from M4s or SAWs, etc.
I had a few that seemed to be somewhat oversized, i.e. fired from a loose chamber, when I resized them prior to loading. My speculation is that these went through a SAW, but I have no definitive answer. There are no marks on any of the brass that would indicate they were belt fed, this was just speculation on my part.
I don’t have pictures. I held onto the brass for a few days as a macabre souvenier, but ended up pitching them.
Could use pic’s and more details , but…
So far it sounds consistant with brass fired in a loose ( belt fed ) chamber , then squeezed tight , loaded a little on the warm side , and fired in a milspec rifle chamber.
Nothing new , '06 and 7.62 LC can do the same thing. Different guns , same issues.
I would be especially careful about brass from a company that is located fairly close to an OSUT or BCT post. Weapons pool guns get run hard .