I took a few AR's to the range yesterday. I'd been having trouble getting my wife's to run. It just would not run. After shooting holes in a bad magazine, I remembered what you said about bolt carrier groups.

I think I PSA's cheapest $70.00 BGC in it. I pulled it out an swapped it for one of their premium nickle boron coated groups, and now the guns fine. It chewed through the next 60 rounds without missing a beat.

Thanks for sharing!

Good to hear! What was it doing wrong?

It wouldn't lock up. The bolt would randomly decide not to close all the way and would not rotate into the locked position. Sometimes it would go into position with some help from the forward assist, sometime it wouldn't. This is with ammo that's been small base sized.

I guess the two places to spend your money are bolt carrier group and barrel?

I wouldnt say that totally, as you don't have to buy the NM coated carriers and such, but they must be in spec, I trust White Oak on those things, they aren't high, but charge enough to have checked the carriers out and make sure that all in the group is in spec.

My cousin bought a new "coated, match" carrier a while back and it wouldn't work. Someone forgot to drill the gas key but it was staked properly...

DD groups are good.

Last weekend, I took my wife AR, the one with the new BCG, and put it on paper. Previously it wasn't shooting very good, averaging about 4" groups. I was convinced the issue with the barrel, which I was ready to turn into a tomato stake. Since then the only other thing I did with it was spend an afternoon with the daughter shooting rocks with it, where I put about 300 rounds down the barrel.

So, last weekend, lo and behold, it broke an inch with several different loads. I was surprised, but happy.

I also shot the rife the new BCG came out of, and those groups seemed to open up a bit.

I think I'll pay a lot closer attention to my choices in BCG's in the future.

My son has given me a new PSA complete lower and I'm starting to finish this gun off. First AR for this old phardt. We were just looking at BCG's on line Friday. I see 'em for as low as $70.00. I don't want the rock bottom units, but can't go full blown premium either. Could you guys in the know suggest a couple to consider from the "mid range" spectrum of things? I'd like to keep the budget for the BCG in the $100-$150.00 range. Thanks guys.

If you need to know, the upper will be a 16" mid length, once again not a bargain basement special, but not a top end custom either.

I got a stag 6.8 that works fine, maybe their 5.56 works as good. It was about $120 with the M16 carrier IIRC. For a "home defense" gun I would get a DD and pay the $200ish.

White Oak if it matters to me... they won't charge more than they have to, so you won't be paying for name brand crap... but they will make sure what they are selling is right.

I'm sorry but the only way they will know if it is right is if they shoot it with your barrel. You're still taking chances.

The "bad" BCG probably was just a bolt not seated straight into the barrel extension/case head which is the only thing that the bolt would have to do with accuracy. once worn in or lapped in to a square fit with the case head, it might start shooting right. That's another reason they say not to swap bolts between guns.

So, given what TWR said, what about using 1 bcg between 2 uppers on the same lower?

I have a 20" bbl flattop upper and a 16" bbl with sights.
Am I causing premature wear by swapping the bcg between the 2 uppers?

Thanks
Mark

Yes you are. The bolts wear into the extension and there will be minor variations from one to another. Depending on how much you shoot, you may never see a problem. But if you want the best accuracy, let one bolt wear or seat into one extension.

No different than lapping the lugs on a bolt action rifle. You wouldn't use the same bolt in two different bolt rifles even if head space was good on both

Bolts are cheap.

I think it was Bob Whitley that told me that those extra-power extractor springs/grommets have a significantly negative impact on the accuracy of AR rifles. Try a standard bolt from someplace that doesn't set them all up to be used in carbines.

David Tubbs lapped a bolt in a buddy's Colt and turned it around. That's when I started paying attention.

Carbine gassed guns are the only ones that need extra power extractor springs, in fact a rubber o-ring added to a mid- length can cause issues. They all need a good extractor.

My take on this, if you have a barrel set up correctly and a bolt that is a good one, it seems not to really matter much. We swapped stuff around quite a bit at times... and never saw a degradation in accuracy. Obviously we were not talking top line accuracy, ours only was chasing about .5 moa more or less.

Were I to after an AR for .25 moa... yes by all means do all you can.

Tubb ain't no dummy either.... we know that.

AIM surplus makes a Nice Nitride MPI Tested full auto bolt for 89 bucks. free shipping, comes Highly recommend on the AR 15 forums.. I have assembled rifles with these Bolts and they all functioned flawless and are properly staked.

I've seen those in emails from them pretty regularly. Thanks for the info.

Thanks KMM

I had one with the same issues described in the OP. Removed the O-ring from the extractor spring, and no more issues. Nothing wrong with the BCG; the stiffer extractor spring was shaving brass on closing bad enough that a stray sliver of brass would prevent lockup occasionally.

My experience is that a correctly tuned gas system of any length doesn't need an O-ring. That means making sure it's not over-gassed of course.

Lapping the bolt may help, but the key is headspace. A properly headspaced bolt in a good barrel will maximize accuracy.

Bump for TikkaNut.