I'm putting together a 300 blackout pistol upper and ram into a problem. I bought a pre assembled PSA upper and a PSA premium bolt. Well the bcg without the barrel installed is extremely tight in the upper about where it gets to the ejection port. I checked against my other rifles and it's excessive. I checked a YHM bcg and it slides fine, same for the PSA bcg in another rifle.

I assembled the upper and tried again with it on a lower and cycled it by hand about 100 times or so. Still extremely tight, tight enough that it won't go fully into battery by releasing the bolt catch with a empty mag in it.

Again the YMH bcg works perfectly in it. And the PSA bcg works fine in my YHM rifle. The PSA bcg is beautiful, slick, nickel boron finish, no defects that I can find. The YHM bcg is phosphate coated and has <300 rounds on it.

The upper showing witness marks where the 2 upper wear rails ride from the bcg be side the gas key.

Think there is any issues running it with the YHM bcg being it chuckles fine by hand? It almost seems as if the chucked it in a clam shell block and it tweaked the upper in a hair around the ejection port.

Anyone else ran into this?

Have you contacted PSA?

Would that cause the upper to wear, rather than the Bolt carrier?

I have seen this once with an AIM BCG. It just slipped thru QC. PSA will swap that out. I would not wear your upper to fit an out of spec BCG. PSA customer service is very good. You did the right thing by double checking with other uppers and other BCGs.

No I haven't contacted psa, I just finished it at 11pm last night. Been on the road today.

Even though the PSA bcg cycles correctly in the YHM rifle and the YHM bolt cycles correctly in the PSA rifle, contact them about warranty?

I was dying to shoot it this weekend

I got chance to call PSA, they said sounds like the bolt is out of spec. Also said if it functions fine in the other rifle and I was ok with it just to leave it switched in the other rifle. Said I have have 30 days to return it and they would swap it with another bolt, fired or unfired didn't matter.

I'm picking up some ammo Saturday am to try it, unless there's a good reason not to.

It's up to you, but I would return it as they said it might be out of spec. I wouldn't take any chances on it unless you have head space gauges and what not. I mean there is an explosion going on over there, better safe than sorry.

I agree. Really no reason to keep a known out of spec item. That is not what you paid for.

Well, over 150 rounds thru both guns no problems with the bcg's swapped. Learning to shoot a 300 black pistol at distance with reasonable speed and accuracy has been a challenge.

I bought a PSA NiB BCG a few years ago. Hand cycling it wouldn’t go into battery at first. After the first range trip it was GTG.

This is really a dumb reply for you. Have you stripped, cleaned, and lubed the Bolt & carrier with good oil & Lube? I had one like that, it was so stiff I couldn't even pull the bolt out so I stripped it including the ejector & extractor, soaked and cleaned it well with breaf free. A couple drops of pro-shot friction proofer on the gas rings , lined um up and then used tw 25 every place else. Put it all back together and cycled the bolt in and out of the carrier maybe a thousand times by hand. That one is so smooth now you can follow the round with the charging handle and then a light nudge on the forward assist locks the bolt. Never hurts to clean and lube um anyhow.