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First AR Build (for myself that is)

Very nice. Doesn't look like there are any problems
 
John A. said:
Very nice. Doesn't look like there are any problems
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nothing major. excessive brass on the deflector to the point its clear the bcg speed is too high even with .223 so i have a spare spikes buffer coming from a buddy that should take care of it. last shot hold open doesn't always engage. haven't had a chance to test with my buddy's pmags but i suspect something else is going on since my rebuild prebans have new magpul followers so they should hold open. worst case scenario the bolt catch is out of spec and i'm sure aero precision will take care of me.

i have a $10 copy of the magpul afg2 on the way and i'm waiting for bcm to have their keymod rail covers in stock because the way its set up my support hand is right at the gas block and with the amazingly small diameter of the bcm kmr rail it gets pretty hot after a mag dump or 2 lol i never wear gloves shooting but thats my solution for now.

so that's one thing to consider, the 14.5" barrel with mid length gas system is so soft shooting i love it but most people will have their hand over one of the hottest spots compared to a carbine length gas system that has the gas block further back on the barrel but has a lot harder recoil.
 
The bolt hold open issue may be due to being overgassed, which you could remedy with a heavier buffer, could be a weak mag spring too. I have also seen too much anodizing and grittiness on the lower cause the bolt hold open not to move free enough to work all the time.

Just a few things to check, but with checking with a new mag, you're on the right track.
 
you know thats why i love quality forums, i hadn't even thought about the carrier speed causing the hold open issue but it makes perfect sense. it holds open sometimes, doesn't other times, and sometimes it catches so lightly that seating a new mag drops the bolt. the springs in my gi steel mags are brand new so i will test with new pmags but i doubt it will
be a mag issue. the lower came from aero with their factory ambi catch installed and an empty mag holds open with the charging handle every time and with the upper separated i can clearly see the follower easily pushes the catch up. i'm confident the heavier buffer will take care of both issues, thanks john!
 
A quick google search resulted in this thread.

http://sigtalk.com/gun-projects/24685-ar-bolt-not-locking-back.html

I think you should give it a read as this fella has the EXACT same issue. In short sounds like your lower also wasn't possibly milled properly for the ambi catch. That thread is very recent so sounds to me like Aero might have a bum batch of those out right now. Might require a call to Aero about a possible fix/replacement. Based on what they were saying in that thread I don't think playing with buffer weights is going to have any impact here but your welcome to try first. If it is in fact defective Aero should be forced to make it right especially if they have more than one customer on the horn barking up the tree about this issue.

Good luck.
 
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hmmm thats very interesting. i'll have to check and see if the catch arm protrudes above the top edge of the lower at all. if it does i'm going to email pictures to aero but with serial numbers and the hassle id rather just cut modify the catch arm or notch my upper slightly then wait for another lower, strip this one down, return it, and rebuild the new one.
 
ok, went to the range for some troubleshooting. with the upper off no part of the catch rises above the top surface if the lower. all my mags did it but its happening less and less and won't do it if you fire a single round. so i'm still thinking the carrier speed is probably the culprit. once a heavier buffer is in and i give it a good run i'll update.
 
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