Headspace Issue?

TGR · Aug 17, 2018

New 300 Blackout build with Aero Precision Upper/Lower, BCA Barrel, and Prime Weaponry BCG.

When I check headspace with Clymer Guages it will not close on the GO or the NO-GO gauge. The bolt closes with resistance on a factory round but leaves marks (not dents) at the shoulder.

I swapped the BCG with a Bushmaster BCG from my competition gun. Everything works perfect. Closes on the GO, doesn’t close on the NO-GO and closes normally on a factory round.

Should I return the BCG? Will it break-in after a short period of shooting?

Suggestions?

qorban88 · Aug 17, 2018

Bad BCG, do not fire.

Allen65 · Aug 17, 2018

It's not the entire BCG that's the problem, just the bolt. It doesn't headspace, and that's a safety issue. You're mixing one company's bolt and another's barrel and either one or both (i.e. tolerance stackup) could be very slightly out of spec, causing the headspace problem. The bolt, barrel, or both, should be returned unless you have a chamber finish reamer handy.

TGR · Aug 18, 2018

Allen65 said:
It's not the entire BCG that's the problem, just the bolt. It doesn't headspace, and that's a safety issue. You're mixing one company's bolt and another's barrel and either one or both (i.e. tolerance stackup) could be very slightly out of spec, causing the headspace problem. The bolt, barrel, or both, should be returned unless you have a chamber finish reamer handy.

That’s what I figured. I’m going to send the BCG back since I bought it assembled and have them send me a new one. Hopefully fixes the issue. In the meantime, I’ll see how it shoots with the Bushmaster BCG.

Thanks.

jrumann59 · Aug 22, 2018

I would not buy a BCGs from just anyone. With the surge in the market from Obama and some of the recent rhetoric, there are literally companies popping up every day many of which are selling "cheaply" priced stuff which is actually Chinese junk and actually ripping you off. Toolcraft is the preferred AR maker of BCGs, There are few others but Spikes, BCM, PSA, brownells, midway, optics planet, Joe Bobs are far better places to buy a BCG because they have been around a while and will not purposely sell you Chinese junk. Also be doubly careful with coated BCGs mainly NiB (nickel boron) some BCG makers do not make sure the their part the BCG is machined slightly smaller to accept the coating layer so it can also push a part out of tolerance.

TGR · Aug 28, 2018

Well. Got a new bolt. That one didn’t headspace either. So it’s the barrel. Primary Arms already shipped me a new BCA barrel. It’s on the mail now. I’ll let you know how it goes.

lee2 · Aug 29, 2018

are you removing the extractor and ejector?

bmorewineguy · Aug 29, 2018

TGR said:
Well. Got a new bolt. That one didn’t headspace either. So it’s the barrel. Primary Arms already shipped me a new BCA barrel. It’s on the mail now. I’ll let you know how it goes.

Are the bolts coated in Nickle Boron or chromed? Sometimes they won't headspace on a tight but in spec chamber which could be why your other bolt headspaced.

TGR · Aug 30, 2018

Bolt is stripped when checking headspace. Two bolts failed (one Nickle Boron and one not) the one bolt that passed was a used bolt with about a 1000 rounds thru it. The chamber felt tight when chambering a round and I think was reshaping the shoulders a slightly. In my opinion the chamber is out of tolerances, but we will see when the new barrel arrives.

clandestine · Aug 30, 2018

BCA Barrels have this issue often.

I usually have to lap them.

Remove the upper and BCG. Manually insert a live round in the chamber and seat it as far as you ca can with your finger. Once fully inserted into the chamber the round should be able to be shaken out or pushed out with a cleaning rod from the muzzle with little resistance Some have chambers that are not round or too small diameter wise.

biermkr · Aug 31, 2018

Stainless or chrome moly barell?

TGR · Sep 2, 2018

Chrome Moly

TGR · Sep 5, 2018

Ok. Got the new barrel from Primary Arms. With a little effort, it headspaced. BCA specs musts be on the tighter side. Things worked in together fine with some working of the action.

I ran 5 different loads thru it from 220 subs to 110s without a hiccup. Have to say the BCA barrel was pretty darn accurate with a 5 shot group of 0.56 with factory ammo and a Red Dot at 50 yards.

The Bolt Carrier Group from Prime Weaponry worked great. Great workmanship, staking was well done, NiB looks great. They had great reviews, not the cheapest, but thought I’d give them a try since it looked like quality workmanship. I think it’s going to be a good setup.

Thanks for the info guys

Magnumite · Sep 6, 2018

clandestine said:
BCA Barrels have this issue often.

I usually have to lap them.

Remove the upper and BCG. Manually insert a live round in the chamber and seat it as far as you ca can with your finger. Once fully inserted into the chamber the round should be able to be shaken out or pushed out with a cleaning rod from the muzzle with little resistance Some have chambers that are not round or too small diameter wise.

Resharpening the same chamber reamer a little too much, maybe?

Headspace Issue?

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