AR accuracy issues, order of likelihood

I’ve been having issues with an AR build for awhile now. It’s a 16”. I am on my 3rd barrel now and I will absolutely give you I’ve been buying cheap barrels and it seems like this build just happens to have gotten all of the bad ones and I’ve lucked out with all other builds. Or that seems to be the case so far.

First barrel was generic HBAR no name from Brownells for $40. Won’t complain. it shot 3-4MOA. I wanted something slightly nicer. I got a fluted HBAR from Classic (according to them, BCA is their contract manufacturer). I waited a long time to install the barrel and when I finally did it shoots 3-8MOA. They won’t warranty it because I waited over a year to talk to them about it.

Well I ordered a barrel from BCA direct this time. 4-10MOA now. This recent barrel maybe the optic has crapped itself, but the last barrel I tried even with my known good 3-9 scope that shoots sub MOA with the right ammo on my 20” and still horrible accuracy.

Emailed them yesterday and if I don’t hear back I’ll call them by Wednesday. They do have a 1 MOA guarantee on their barrels. And I tried a lot of ammo types and the best I could manage yesterday was a 2.04” center to center 5 shot group at 50yds... it was with IMI M193. Next best was Hornady 55gr match at 2.13” group size. Federal XM855 and PPU M855 were the worst at around 5” groups at 50yds (and tried half a dozen other weights and brands).

I head spaced things and it won’t close on a foster no-go gauge and takes force to close on a go gauge. Which seems suspiciously tight, but the brass has no pressure signs on it. The last barrel swallowed the go that’s fine and wouldn’t take the no go gauge. I tried with my other BCG and same behavior for the gauges. I can drop the bolt (which I don’t like to do) and it’ll go in to battery. It won’t by easing it down or with the gauge set over the extractor and eased in to the chamber. Takes a whack of my 4oz rubber mallet to get the lugs to rotate and I have to very lightly mortar it to get the gauge back out of the chamber. Hand pressure and taps with my palm on the forward assist aren’t enough to get it in to battery.

Both barrels seem a little loose in the upper receiver prior to tightening the barrel nut, but not crazy loose.

I didn’t try my other BCG with this barrel at the range, but the other barrel I did and no effect on groups.

The lower is used with my 20” upper which shoots 2MOA with most cheap ammo and 1 or a little under 1 with match ammo.

So I am pretty much down to a string of bad luck with barrels or some issue with the upper receiver. For the heck of it I ordered a couple more upper receivers since primary had Anderson uppers on sale for stupid cheap yesterday. I’ll try a completely fresh build for the upper if I can get BCA to swap the barrel or if not try the barrels I have on hand in the new uppers.

Any one have any thoughts? Anything I might not be thinking to check? AFAIK I am doing all “best practices” on assembling the upper. Gas key slides over the gas tube without resistance. Gas block is indexed out from the barrel shoulder by a couple sheets of paper. Torqued then loosened and then tightened down the barrel nut 3 times and its set to 42ft-lbs for final torque to index the barrel nut properly for the free float handguard (NSR style eBay special). Gas key properly torqued and staked on the BCG.

Did you lap the receiver face? Your receiver may be "not true" and that could be part of the issue...

We SOTAR persons also "bed" the barrel extension with Locktite 620, to remove any excess space between the barrel extension and receiver......

That being said, with lower end barrel's, great accuracy may be tough....

I too had "bad luck" with BCA barrels. I think that they might be crap. I ordered a good one from Faxon and shoot sub moa.

I cant speak on the brownells but ive tried 2 classic barrels(16 HB stainless fluted, 7" stainless). Both had horrible crowns. 16" never shot better than 3moa and 7" made my shotguns look like sniper rifles. My friend bought a 16" stainless HB that shoots 4" groups @ 50 yards. 7" was so bad at an indoor range i accidentally shot the target of the guy in the next lane. By comparison, I next used a fulton armory 20" chrome lined HB that shoots 1.25"@100 with federal 5.56 m193 so its not me. One thing i will say to watch out for is overtightening the barrel nut.

Yup, receiver extension is lapped. I didn’t bed the barrel because I didn’t want to run in to not being able to get it back out easily. I figured if it shot fine, I’d bed it at that point.

I guess maybe I just had a few lucky barrels. My 18” Grendel barrel from classic is a 3/4” gun and I had a 10.5” pistol barrel from them that was 2MOA with a 3MOA red dot and crappy ammo all day long.

I am going to try to get this “fixed” if I can with them. I don’t need a 1MOA rifle for my 16” AR. It’s for plinking, bump in the night and if some some reason something is messing with my chickens that a 22lr isn’t going to solve. But nothing worse than 2MOA with match ammo would be nice and not worse than 3 with at least some 55gr FMJ.

Anyway, if I can’t get this fixed with BCA my lesson is learned and I am just going to get a faxon barrel.

Buying the cheapest barrel you possibly can and having it shoot 4 MOA is a testament to the AR15. 4 MOA is a good day for an AK clone.

+1 for Faxon barrels. Buy once, cry once

Overall sounds like bad QC at either end of the barrel, but here's a couple more ideas to consider:
Check to see if the rounds are getting chewed up on their way to the chamber. Are you using a muzzle device on these barrels? If so have you been using the same muzzle device on these barrels? Try shooting without if you're using one.

My favorite cheapo barrels are from Rosco. So far they have been accurate and reliable.

fbi_surveillance_van said:

Overall sounds like bad QC at either end of the barrel, but here's a couple more ideas to consider:
Check to see if the rounds are getting chewed up on their way to the chamber. Are you using a muzzle device on these barrels? If so have you been using the same muzzle device on these barrels? Try shooting without if you're using one.

My favorite cheapo barrels are from Rosco. So far they have been accurate and reliable.

Click to expand...

The classic barrel the bullets saw a bit of marking on them, but barely able to feel it with a finger nail. This one I didn’t check, but will.

Same muzzle device on all of them, A2 birdcage. I’ll try it without it on. I’ve been thinking of going Black River linear comp. I love my KAW Valley comps and I’ve been sticking them on all my ARs. But for the 16” I wanted something with some flash suppression. The KAW comps don’t seem to suppress flash at all. The BRT comps supposedly do and the few videos I’ve seen of them, they seem to suppress flash close to as well as an A2 flash hider does.

I’ll look more closely at the receiver feed ramps and barrel feed ramps. I suppose it’s possible that’s tearing up bullets, but the marks on the Classic barrel didn’t seem bad enough to really screw with accuracy.

On the over tightening I’ll admit until recently I’ve been using a wrench and long time mechanic calibrated torque specs, “that feels like it’s about 40ft-lbs”. I did finally get proper crows foot wrench and used my torque wrench this time. Set it to 35, tightened and loosened 3 times, then set it for 42 and tightened it down. Used aeroshell grease.

My plan is, assuming BCA replaces this one, build two otherwise stripped uppers with the classic barrel and the BCA barrel (I’ve got the extra gas system parts and hand guards) once the new Anderson uppers show. Leave off the A2, see how they both shoot in new uppers. Will try the bolt that’s in there and the bolt from my 20”.

Ramps seem like a smooth transition. Chambered a round and ejected it on to some carpet. Looks like it is sitting against the rifling. 5.56 round (IMI) and supposed to be chambered .223 Wylde. That seems like the throat is too short (which jives with the head space being overly tight, but at the edge of spec?)

The marks on the bullet have a slight spiral. Cosmetic shiny, but one is deep enough I can feel it with my finger nail (barely, but I can).

Popped primers on some of these? The primers do seem flatter than some of the other fired brass I have laying around that I know went through my 20” that runs great.

Instead of speculating over the internet , it needs the full Chad/ SOTAR inspection and gauging .

Cheap barrels make great tomato stakes from what I hear. Buy a guality barrel !

Buy a Krieger/ end thread!

Anderson can be hit or miss, lots of out-of-spec stuff, but BCA isn't hit-or-miss, it's basically just miss, most i've seen shoot like crap, and have spec issues with basic things, in your case extension fit and headspace, possibly more. Cheapest I usually go are Ballistic advantage or Faxon, still the occasional issue, frequently tight headspace, but most shoot well, and they are quick to address problems. Might be able to build a <$500 AR, which is amazing, but have to keep realistic expectations.

dist1646 said:

Buy a Krieger/ end thread!

Click to expand...

He's right ya know...

I hear Criterion is excellent if you're going to switch.

Some of those casings look like they have ejector swipes, and the popped primers are not normal.

What is the spec for the GO gauge you are using?

What is the firing pin protrustion reading?

What size is the has port?

Is the firing pin hole too large?

Have you manually loaded rounds to isolate feed geometry issues?

What trigger is in the lower? Using aftermarket springs?

Using KNS Pins?


None of these questions factor in a short throat or bad crown.

clandestine said:

Some of those casings look like they have ejector swipes, and the popped primers are not normal.

What is the spec for the GO gauge you are using?

What is the firing pin protrustion reading?

What size is the has port?

Is the firing pin hole too large?

Have you manually loaded rounds to isolate feed geometry issues?

What trigger is in the lower? Using aftermarket springs?

Using KNS Pins?


None of these questions factor in a short throat or bad crown.

Click to expand...

The time that I had complicated problems with my AR 308, I saved a bunch of time and money by taking the rifle to Chad, whose rates are incredibly reasonable for what you get. Also it was a highly educational experience, one which you probably will not get from any other gunsmith. I don't think I've built anything since that rifle, but in the future I'll probably limit myself to parts he recommends unless I have a pretty good reason.

clandestine said:

Some of those casings look like they have ejector swipes, and the popped primers are not normal.

What is the spec for the GO gauge you are using?

What is the firing pin protrustion reading?

What size is the has port?

Is the firing pin hole too large?

Have you manually loaded rounds to isolate feed geometry issues?

What trigger is in the lower? Using aftermarket springs?

Using KNS Pins?


None of these questions factor in a short throat or bad crown.

Click to expand...

Foster go gauge. 1.4636”

I’ll have to check the protrusion later, but it has never caused primer issues on the other two barrels I’ve tried (granted neither of those were running accurately either, but bigger issue with the current and last one). Same with gas port size and firing pin hole.

I’ve manually loaded rounds by dropping them in the chamber and closing the bolt and then holding the rounds as they come out so they aren’t dragged against the lugs.

My stoner 20” barreled rifle, a 20” classic barrel and the earlier 16” BCA barrel all swallow an IMI 5.56 with no noticeable marking on the brass. The short headspace barrel leaves two small brass rifling marks, but cosmetic only, fingernail rides over them without catching. A Hornady .223 round seems to not have marks on it. All combos the bolt closes easily on the round with gentle finger pressure on the bolt (operating it with the upper off the lower). Assembled all combos accept the short headspace BCA barrel the bolt will close with between finger pressure (stoner barrel) and slight pressure on the rear of the bolt. The short headspace barrel I can hit the back of the BCG hard with the palm of my hand several times and it won’t go in to battery. It takes my 4oz rubber mallet hitting it medium hard a couple times and then mortaring to get the gauge back out.

All barrels if I put a .223 or 5.56 round in the chamber and press it in with a pound or two of force with my thumb and turn it upside down it takes a light bump on carpet and the round will fall out of the chamber. Doesn’t seem to be any real difference there.

If attempting to close the bolt with the barrels off the rifle a similar experience. The stoner barrel it’s very light pressure to twist the lugs in to full engagement with the headspace gauge in the chamber. The other two mild to moderate pressure and the short head space barrel it takes a fair amount of force.

It is a Larue MBT trigger that otherwise appears to work perfectly. I use this lower with my 20” stoner upper for subMOA results. I am using the light spring.

Trigger and hammer pins that came with the MBT.