mpk1996 Posted September 4, 2014 Share Posted September 4, 2014 So, I was out at the range shooting my M4. I had the range to myself, so the drills I was running were going pretty fast. After about 30-40 min of shooting after I finished one of my drills I went to put the rifle back on safe, but it would not go. I flicked it back to fire, operated fine. Same with full auto, but it wouldn't go on safe. So i dropped the mag and cleared the rifle, pulled the take down pin to have a look. nothing out of place. nothing broken that I can see. So I took it over to one of the Bravos to get a punch to start breaking it down. first we pulled the auto sear to see if that was in the way some how. Nope, sill wouldn't go to safe. so we pulled the trigger and then the safety. As we get the trigger out and roll the safety out, a spend primer, yes primer falls out. I guess running 8-10 mags in relatively fast order had heated the rifle up to the point where the brass was expanding enough to loosen the primer pocket. And on extraction and ejection the primer fell out and got wedged under the safety. pretty interesting, as I had not see that particular failure before. just figured I would share Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted September 4, 2014 Share Posted September 4, 2014 Thanks, MPK, I'll be looking out for it in the future. Appreciate it. Link to comment Share on other sites More sharing options...
kurtm Posted September 4, 2014 Share Posted September 4, 2014 The primer cup is brass as well and if heated would expand at the same rate the pocket would and would not fall out. With that much heat, more than likely, a cartridge became over pressured due to the powder charge being real hot and it blew a primer. It happens, not often, but it does happen and the primer and anvil can end up in the darndest places. Weirdest one I ever say was an anvil that got shoved into the gas key and the rifle wouldn't cycle right. Took forever to find it! Link to comment Share on other sites More sharing options...
mpk1996 Posted September 4, 2014 Author Share Posted September 4, 2014 The primer cup is brass as well and if heated would expand at the same rate the pocket would and would not fall out. With that much heat, more than likely, a cartridge became over pressured due to the powder charge being real hot and it blew a primer. It happens, not often, but it does happen and the primer and anvil can end up in the darndest places. Weirdest one I ever say was an anvil that got shoved into the gas key and the rifle wouldn't cycle right. Took forever to find it! could be, not sure what exactly happened. just know the primer ended up under the safety. ya, lots of moving parts and things going quickly. Link to comment Share on other sites More sharing options...
Vlad Posted September 4, 2014 Share Posted September 4, 2014 Weirdest one I ever say was an anvil that got shoved into the gas key and the rifle wouldn't cycle right. Took forever to find it! Funny you should say that, I've seen one like it recently too. Link to comment Share on other sites More sharing options...
fiddler Posted September 4, 2014 Share Posted September 4, 2014 Somebody makes a little rubber thing for the bottom of the reciever that is supposed to keep primers from fouling up the trigger. Must happen often enough. Link to comment Share on other sites More sharing options...
MickB Posted September 4, 2014 Share Posted September 4, 2014 On a 9mm Colt AR15 I once ended up with an empty case crushed behind the hammer that locked up the trigger group... Mick Link to comment Share on other sites More sharing options...
dauntedfuture Posted September 4, 2014 Share Posted September 4, 2014 Were you shooting M855 or M855A1? Link to comment Share on other sites More sharing options...
MarkCO Posted September 4, 2014 Share Posted September 4, 2014 I have seen that failure quite a few times. I highly doubt that heat had anything to do with it though. Link to comment Share on other sites More sharing options...
openclassterror Posted September 4, 2014 Share Posted September 4, 2014 Just recently had a customer buy a lot of PMC ammo- entire lot was way over-pressure. Probably about one out of every 30 rounds popped a primer, whether rifle was hot or cold. Chamber was 5.56, not .223, so tight throat was not the cause. Link to comment Share on other sites More sharing options...
goldfieldshooter Posted September 4, 2014 Share Posted September 4, 2014 Check out the Reloading Forum (rifle and shotgun) and you will see it is not an isolated occurance but quite common. Link to comment Share on other sites More sharing options...
GreenDragon64 Posted September 4, 2014 Share Posted September 4, 2014 I had a cup wedge itself behind the gas key between it and the charging handle that locked it up pretty tight with the bolt about half way back. Link to comment Share on other sites More sharing options...
Currently Posted September 4, 2014 Share Posted September 4, 2014 Hot sunny day, mags on the table soaking up heat, couple of mag dumps and something happened to me. Link to comment Share on other sites More sharing options...
Ranger6 Posted September 5, 2014 Share Posted September 5, 2014 Saw this happen at a training session conducted for some USAF Pararescue (PJs). Ammo was mil-spec issue. One caution: Do not handle with ammo in the M4. You can put it into "full auto" and burn a magazine load. Ranger6 Link to comment Share on other sites More sharing options...
gerritm Posted September 5, 2014 Share Posted September 5, 2014 Had this happen to me a couple of matches ago with Federal XM193 on a very hot Texas day. Kind of a fast stage, got about 10 shots in and my CMC trigger locked up tight with no movement. Went to the safety table and took it apart and a primer cup fell out of the the trigger housing. gerritm Link to comment Share on other sites More sharing options...
Graham Smith Posted September 5, 2014 Share Posted September 5, 2014 http://www.midwayusa.com/product/970550/dpms-molded-receiver-rug-ar-15-mil-spec-trigger-rubber-red Link to comment Share on other sites More sharing options...
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