Blown primers and other malfunction troubleshooting
I had some issues yesterday that I don’t understand. Would appreciate any help in getting it sorted out. I’m real bad about diagnosing malfunctions in the moment since I usually just go into immediate action but some of what I recall seems very odd.
Barrel: 12.5 Criterion Core
BCG: Geissele REBCG
Ammo: 56gr 5.56 MEN
Mags: multiple Gen M3 PMAGs and USGI
Buffer: A5 w/ standard rifle spring
Can: KAC 5.56 QDC
Upper’s total round count: 399
The upper was pretty new with only 204 non-suppressed rounds on it before the class. Those rounds were a mixture of cheap brass cases .223 so this was my first time with the MEN in this gun. The malfunctions started towards the end of the day after about 120 rounds. I kept the can on until I started having issues.
First malfunctions were failures to feed from three different mags. It didn’t look super dirty but I initially assumed that was the issue since I had a can so I just added lube and kept going. Then I had a mixture of blown primers and rounds stuck in the chamber. The first primer lodged itself in between a lug in the barrel extension and the case’s rim, so that the round could not be fully chambered. I had to use a knife to pry it out. I then removed the suppressor and within the next mag or two, had another blown primer. I don’t remember the exact reason but the gun just felt weird when cycling so I stopped shooting and looked. The primer was in between the bolt and bolt catch, stopping the BCG basically at the rear of the cycle. This primer was dislodged by pulling the CH back.
The last was an unfired round in the chamber. I don’t remember why I stopped shooting or what even tipped me off about it, but for some reason, the bolt was locked back (I very well may have dropped the mag and locked it to the rear). I do know that I glanced into the chamber and was very surprised to see a round fully seated with no mark on the primer. I let the bolt go (don’t remember if I did this gently or just dropped the bolt catch), pretty sure I pulled the CH with nothing and then dropped the CH and again pulled it and this time the round was extracted.
I know blown primers can be a sign of over gassing but I had the barrel gauged before JT @ RAW assembled it and think it was .068 which seems reasonable. I know MEN is supposed to be hot and based on estimated velocity yesterday, it was, but am surprised by the mix of blown primers and failures to feed.
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Blown primers and other malfunction troubleshooting
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Quick shots of the BCG. It’s not clean but that should still be functional right? There was a lot of gas blowback in their promo vid which is interesting. I didn’t notice any the entire time except for the first 2-3 rounds right after I dumped lube on it.
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