Rookie here. I just assembled a Gen 3 PSA AR-10. I fired the first 20 rounds through it from a brand new 10 round PMAG. Twice I had a failure to feed. At the time it had zero lube.
Is this a rifle issue, a mag issue or an operator issue? 
Ideas for fixing it?
Lube wouldnât hurt. 20+ round capacity mags wouldnât hurt either because freedom.
Lol. Well brother I wish it was that easy. Here in California 10 round is best I can do. Wouldnât want to get caught with a higher capacity mag and lose my CCW.
I figured. I was just messing with you. I live in a freedom state and run 25 and 10 round P mags and 20 round hex mags with no problems in a DPMS 10 and havenât heard of anybody having troubles with P mags in a PSA or any make.
What ammo were you running? Giving it a good cleaning and light oiling couldnât hurt anything. Iâm assuming it is a complete upper, what do you have for a lower?
Itâs all PSA. I assembled the lower but bought the upper already assembled. The ammo was factory but not sure what brand at the moment. Maybe Federal in a white box?
Thatâs pretty reliable ammo, what exact lower/kit?
https://palmettostatearmory.com/psa-pa10-moe-ept-lower-build-kit-black1.html
https://palmettostatearmory.com/psa-gen3-pa10-stripped-lower-receiver.html
Did you clean it before you shot it? I ask because itâs new and new parts are coated with factory slim, so itâs a good idea to clean new equipment.
I didnât clean it. I figured it should work right out of the box. I didnât notice it having significant grease on it or anything. So now I lubricated the bolt carrier and am going to try again in the next couple days.
AlrightâŚhere is the solution:
First, lube it up. Arâs are meant to be wet.
Second, welcome to the world of 10rd pmag issues. The solution is 10 min and sandpaper. For some reason, when magpul designed the 10 they put a bump on the back of the mag. This bump interferes with a variety of ar10 lowers. They dont do it on the 15, 20, or 25 rd. So you need to sand the bump off.
Sand here:
Until it looks like this:
The bump makes the mag seat at an angle, with the back down and you get the bolt jumping over the rounds instead of stripping them.
Wow. Okay there is a tiny bump or âledgeâ there. I will try that ! Seems like a cheap fix. : )
Thanks GuitarGuy !
@chrishajduk welcome. Report back if that works.
Will do ! Gonna be a few days.
IMHO, donât get caught up in the PMAG craze. The HexMags work great in my PSA Gen 3 AR-10 (308) and they are a little cheaper. The 10 round mags look the same as the âstandardâ 25round mags with a limiter in them. Not sure if you can get away with that in Californistan though.
âAll limited capacity magazines feature the True Riser system pioneered by SENTRY. You get a standard size magazine body that has the internals of a shorter magazine so it will look natural in your rifle and fit in all of your gear appropriatelyâ
Hmph. Learn something new everyday. I never had an issue and never did any sanding, but my âbumpâ that I think youâre referring to is pretty non existent on mine. 10 and 25 for comparison.
Slowly load the mag in the magwell and see if it tilts when you get it to lock in. look at where the ledge or bump meets the lower to see if it is making contact.
Edit: your mags are black, mine are sand, which I dont think Magpul makes anymore.
Thanks !
Ok. Iâm hoping the sanding fixes it. Worth a shot. I had 2 failures to feed out of 20 rounds.
No bumps on my MagPul 10âs or 25âs, either.
The 25s didnât have them. They have a ledge, but it is well below the bottom of the magwell.
