Need help with 10.5" Pistol trouble shooting

[MistWolf]

Mist, why would you do ammo testing first. Seems like pulling the trigger and doing a proper install can be done at home in 10 min.

Because the problems and analysis of amac's AR are heading off in multiple directions. Each malfunction could have a different source or they could be related. My experience with Remington UMC bucket ammo is that its performance is erratic. Ammo with erratic performance complicates troubleshooting- you won't know if the malfunction is due to the ammo or the firearm.

Performing a lockback check using in spec ammo gives you a baseline performance right from the start. Until a lockback check is performed with good ammo, how will amac determine if the short stroking is related to the trigger problem, the ammo or a gas leak? How will amac know if the trigger problem is related to the short stroking or not?

Successful troubleshooting is a methodical journey taken one step at a time. The first step in troubleshooting an AR is a lockback check using in spec ammo.

[Five_Point_Five_Six]

I gave my son a pistol build kit for Christmas. He assembled a Spikes Tactical enhanced lower kit and added an SBA3 brace. For the upper, I gave him my 10.5% Noveske upper that has been running flawless on my SBR Noveske lower. I've put numerous rounds suppressed and unsuppressed through the upper on my lower. My son took his new Pistol AR to the range today and experienced some failures to feed, failures to lock back on empty and a few times, the trigger wouldn't reset. He didn't keep exact count of failures to successful cycles, but my discussion with him leads me to think maybe 10-15 (maybe a few more) failures out of 200 rounds shot. Not a bad percentage, but not 100% reliable like my SBR.

I don't think it's a gas port issue because the upper reliably cycles on my lower. I'm shelving this topic until I've exhausted everything else.

I measured both buffer tubes and they are the same. I gave him the same buffer spring and H2 weight that I was using. He did switch out to a standard buffer weight and experienced similar issues. He said more trigger related with the standard buffer weight than feeding or lock backs.

He was shooting a "bucket" of Remington UMC 223 ammo purchased from Cabella's. This is my primary guess for "gassing" issues. Maybe this ammo is weak? I will go with him on the next outing and bring various ammo I have on hand. Mostly PMC brass.

Before next outing, I will clean and inspect the bolt and gas rings. I will make sure to heavily lube everything before shooting.

Outside of the above I've mentioned, what other aspects of the failures am I missing and should inspect?

Thanks for the feedback.

Those buckets of UMC are about on par with Tula. It will run in our spare PSA upper with a blown out gas port and a carbine buffer but it won't cycle properly in my BCM or Colt uppers.

[amac]

Those buckets of UMC are about on par with Tula. It will run in our spare PSA upper with a blown out gas port and a carbine buffer but it won't cycle properly in my BCM or Colt uppers.

Lol! That’s a strong recommendation you don’t want logged for your product!

I hope the solution is as easy as quality ammo.

Thanks