The first 300 went smooth using a carbine buffer springs and H2 buffer. In the last 2 range trips I had, I began to experience malfunctions. I had 2 FTF and the bolt is not locking back after the last round. I tried different mags and still the same, I even tried to the 1 round bolt lock check and it is not locking back either. Brass ejection is at 4:30
When I went home, I checked the gas block set screw and it still screwed to specs. I will switch the buffer to a regular carbine buffer and see if that fix the issue.
Is it possible for AR to be undergassed as you put more rounds into it? I am thinking that due to carbon build up it might interfere with the gas flow in the gas block/tube even if I clean my gun after range trips.
I know you checkext the tightness of the gas block, but you may also need to check alignment is still good and there are no obstructions. Stuff a rag in one end of the barrel and use compressed air oj the other. Air ahould come out the gas tube (and upper should be apart from lower and bcg removed).
Range Report: Switching to lighter buffer from H2 is a no go. Did a 1 round test and bolt still not locking back on empty. I checked the gas ring, gas tube, gas key and gas block and all are in good condition. So I think gas leak is out of equation. Which gives me an Idea it’s the extractor. I swapped the extractor spring that came in originally with my PSA premium BCG to a BCM extractor spring and throw the O-ring for safe measure.
Went back to the range and it ran fine, no malfunctions until around 70 rounds or so and it started happening again. It was jamming every 3-5 rounds or so. Could it be the bolt? I took a photo of the malfunction I had. Seems like it failed to eject and it stripped a new round from the mag as the bolt closing back
I did some testing in my work bench, I replaced this bolt with my other working bolt from another rifle. The other bolt was smooth and no tolerance when fitting it manually (charging handle removed) to the barrel extension. While this bolt pic above, is having a very slight tolerance when putting it in and out in the barrel extension.
Could that tolerance be interfering with cycling issues thus having FTE and double feeds?
Posting an update, I got my issues fixed. FTE’s are confirm caused by a bad bolt, I replaced my old PSA bolt with a BCM bolt assembly, I used the old carrier, test fired at the range earlier, one hundred rounds with no malfunctions.
As for the bolt not locking back on empty, it was the Ammo, apparently I’ve been using AAC 55gr 5.56 FMJ in the past 3 range sessions seems like it’s underpowered some rounds can lock the bolt back, some can’t. I switched it up with a PMC X-Tac 55gr.
All mags locked back on empty, it was a good learning experience.
Problems are sure interesting (when they are other peoples) I spent a month trying to figure out why my tack driver .32cal flintlock was having flyers.
Turned out it was a batch of bad patches, every 8th one was about 20% thinner and the ball would hit way off the group.
