AR accuracy issues, order of likelihood

Also if it helps the picture I grabbed of the casings I grabbed mostly bad ones and a couple okay ones. The rate is maybe more like 1:3 are bad and the others good. I’d like to say that was the rate of fliers in my grouping, but it wasn’t. The better groups I’d have 1 or 2 fliers in the 5 that would open a 1MOA group up to 4. The not so good ammo all 5 were just equally spread apart.

Are the primers actually pierced or do they have oil/grime in the firing pin impression? I made that mistake once.

atblis said:

Are the primers actually pierced or do they have oil/grime in the firing pin impression? I made that mistake once.

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Might be grime. They are smaller than the bigger rifles I’ve seen pierced primers on so it’s harder for me to tell (my Garand popped a couple two range trips ago before I polished the firing pin. This time it ran 28rnds and zero issues). Anyway, I’ll q-tip some and see.

I did look at a bunch of pickup brass from the bottom of my recycling bucket that I know was from before this barrel and I didn’t find any that looked like that. The primers were all cleaner looking.

I have a few questions:
1. How are you supporting the gun when you shoot? If the answer is anything besides good rifle bags, that's something to look at.
2. What is the twist rate of the barrel? If it's 1:7, you might try heavier projectiles.
3. Do you have any ability to see how long the throats of the barrels are? Some manufacturers are infamous for screwing up otherwise decent barrels by setting the throats too long. You can sometimes get better results by using cartridges with longer OAL.
4. What scope are you using? What do you have your parallax set to?
5. What exact Hornady ammo did you try?

I tend to agree with the crowd that you are probably better off just buying a Ballistic Advantage, Faxon, or Criterion barrel when they go on sale.

Like erwos, I'm curious what optics you are using and have you tried swapping optics.
I have a couple fluted Classsic Firearms barrels and they are the worse of what I have. (4MOA)
Criterion shot 1MOA with my reloads (68gr SMK) and Federal Gold Medal Match
I also have a Radical firearms upper kit I built from Primary arms 2-3 MOA with generic ammo and 1-2MOA with reloads and federal Gold Medal Match
I personally need front and rear supported from the bench and 9x optics to shoot 1MOA plus a good 2 stage trigger (I use geisselle SSA)

good barrel,good ammo (matching twist rate), good optics, good trigger, good build, good support, good shooter. Can't skip any of these to get to 1MOA

Maybe others have had good luck but my limited (very) experience is that cheap barrels suck, cheap fluted barrels suck even more.

dist1646 said:

Buy a Krieger/ end thread!

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White Oak and Lilja also make very good AR barrels.

lazarus said:

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.

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1.4636 would be for .223 chambers only. If it's a 5.56 or Wylde chamber a 1.4646 is the proper gauge. That difference can cause accuracy issues and pressure signs.

erwos said:

I have a few questions:
1. How are you supporting the gun when you shoot? If the answer is anything besides good rifle bags, that's something to look at.
2. What is the twist rate of the barrel? If it's 1:7, you might try heavier projectiles.
3. Do you have any ability to see how long the throats of the barrels are? Some manufacturers are infamous for screwing up otherwise decent barrels by setting the throats too long. You can sometimes get better results by using cartridges with longer OAL.
4. What scope are you using? What do you have your parallax set to?
5. What exact Hornady ammo did you try?

I tend to agree with the crowd that you are probably better off just buying a Ballistic Advantage, Faxon, or Criterion barrel when they go on sale.

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Long throats in an AR are rare. Manufacters often go too short thinking it's the same as a bolt gun. It screws with consistency.

In AR's that have consistency issues, I lengthen the throat and they shoot better.

clandestine said:

1.4636 would be for .223 chambers only. If it's a 5.56 or Wylde chamber a 1.4646 is the proper gauge. That difference can cause accuracy issues and pressure signs.

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Yeah it’s the foster .223 go gauge marked 1.4636. It is supposed to be .223 Wylde chambered. Sounds like that is probably my problem then if it’ll barely close on a .223 chamber.

Also it’s around a .07” gas port diameter. Which is on the large side for 16” carbine length, but not way above from what I looked up.

Time to send the barrel back, and also get a proper 5.56 go gauge.

erwos said:

I have a few questions:
1. How are you supporting the gun when you shoot? If the answer is anything besides good rifle bags, that's something to look at.
2. What is the twist rate of the barrel? If it's 1:7, you might try heavier projectiles.
3. Do you have any ability to see how long the throats of the barrels are? Some manufacturers are infamous for screwing up otherwise decent barrels by setting the throats too long. You can sometimes get better results by using cartridges with longer OAL.
4. What scope are you using? What do you have your parallax set to?
5. What exact Hornady ammo did you try?

I tend to agree with the crowd that you are probably better off just buying a Ballistic Advantage, Faxon, or Criterion barrel when they go on sale.

Click to expand...

Currently using a Bushnell TRS-25 and 3x magnifier.

However swapping it on to my 20” upper I have zero difficulties shooting 2MOA all day. I’ve also tried the Bushnell Engage 3-9x40 scope that lives on my 20” and the results aren’t notably better with the two problem barrels.

I am using sand bags for front support and hand pressure for the rear. That doesn’t give me problems shooting <1” groups at 100yds with any of the rifles I have that are capable of it.

At this point I am positive it isn’t an optics or shooter issue, but something with the gun. Likely the barrel.

The Hornady ammo is their 55gr BTHP rounds.

I’ve also tried IMI 193 and 855, PMC Bronze 55gr, PPU M193 and 855, Federal XM193, 855 and 223 55gr, PPU 69 and 75gr BTHP, Frontier 55gr BTHP, 55gr FMJ and M193 and 68gr BTHP.

With this barrel IMI M193, PPU 75gr and Hornady 55gr BTHP producer the best results of 4-5MOA (best group out of them was 2.13” center to center and the worst out of them was about 2.55” center to center, but at least of the 2 5 shot groups for each they were relatively consistent). Almost everything else was up at about 10MOA. On the last barrel the results were the same, except it achieved a maximum of about 3MOA with the same best ammos, that one also managed about 4MOA with PMC Bronze.

By comparison my 20” stoner barreled upper achieves a worst of about 4MOA with federal 55gr 223 and xm193 and 855. Just about everything else it eats and manages about 2-3MOA and anything with “match” or BTHP in the name it is usually about 1-1.25MOA. Though it loves IMI M855 for some reason turning in .8” groups with occasional fliers. Speer gold dot 75gr, IMI 69gr and PPU 69gr it’ll turn in .7” groups with no fliers for the first two and about 1 flier in 15 for the PPU that opens it up about half an inch.

Well, if nothing else, I will say that this thread has single-handedly convinced me to never buy a budget-manufacturer barrel again.

erwos said:

Well, if nothing else, I will say that this thread has single-handedly convinced me to never buy a budget-manufacturer barrel again.

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I means me also. At least at this point I am “invested” enough to try to get a working barrel from BCA. And I’d gotten a 24” grendel barrel from them at the same time, so once my uppers come I need to quick build one and test that also. Just so I know if I need to be talking to their warranty department about that one also.

Pinecone said:

White Oak and Lilja also make very good AR barrels.

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I don't believe white oak makes barrels. Mostly uses Wilson's, John chambers them, but don't make them.

Three barrels shooting the same way seems like a low probability. I understand the quality issue so it may very well be the barrels. I would also closely investigate how deep the barrel turns into the upper receiver without the barrel installed and how the barrel nests in the barrel bore. I would also recut then deburr the barrel crown at the muzzle using proper crowning tooling.

I have used a couple non major name barrels and never had those loose of groups. If this is indeed barrel problems, then it is a good lesson. Maybe left overs from the 24 hour a day production during the Obama induced panic?

No idea. The BCG shoots just great in my 20”. I just got back torn he range with the last bad barrel. CF, probably made by BCA nitrided 16” 1:8 fluted SS HBAR. Best group was 2” with Hornady black 75gr. 2.03” center to center at 50yds. 4MOA. A couple of 5 shot groups were sub 1”, and then a flier or two opening the group to 2.5-3”. Most of the groups were simply large (3-4”).

I made sure the barrel nut is on there right. Torqued to 35lbs three times and then tightened to around 40-45lbs got the screw holes on the barrel nut lined up. It’s a free float handguard with an aluminum nut (NSR style). Any chance that could cause it? With the BCA barrel that’s going back I even used a new aluminum barrel nut, never reused and the result was slightly worse.

All barrels are NOT super tight fits in the upper. If it is inserted all the way I’d say the front of the barrel can wiggle up and down maybe 1/4”. They don’t fall in to place. However they are locked down with the barrel nut on. Zero wiggle. I realize under the force of the round going down the barrel and bolt locking and slamming back in to place you want as snug as possible, but I wouldn’t think a loose upper to barrel fit would result in a 4MOA (or worse) upper.

I DID lap the upper.

I can’t think of anything else with the upper that could cause such horrible accuracy other than the barrel. It is just weird to me that some ammos are stacking 2-3 rounds nearly on top of each other and then there’ll be 1 or 2 fliers far out. Though most are just all scattered pretty evenly.

I looked closer at the primers on the. BCA barrel and the CF barrel I swapped back on and just shot. No popped primers, just filth in the firing pin dents. The BCA barrel the primers do look flatter than from the CF barrel.

All groups today were shot with my 3-9x40 engage scope from my 20” upper.

Also I double checked to be 100% sure it wasn’t me, or the scope.

Oh also the BCG. I used the PSA parked BCG from my 20” for some groups and back to back with the Brownell’s nitrided BCG and the group sizes were within the margin of human error (or at least sample size).

I also then shot a group of PPU 75gr BTHP out of the 20”. First shot was a flier, but that 20” was cleaned throughly and stored for the last maybe 6 months and of course cold bore. So I am willing to discard that. The next 4 shots all stacked. .53” at 50yds. I was shooting off sandbags rather than bipod and rear bag (I usually tighten my groups up a tenth or two that way). With it it was 1.6” group at 50 in case it matters. I regularly shoot 1-1.5MOA with PPU 75gr and the 20”.

So sure as heck not the lower unless it is only some incompatibility between the lower/parts and that one upper.

Could the gas system be causing the issue? Seems really crazy that it could be. Or at least accuracy that terrible. Everything cycles just fine.

Either way, I called and BCA sent me the return label right away, so the BCA barrel is going back and I’ll just have to feel good enough that until I can get an ACCURATE barrel on there, with the CF barrel is still better than minute of man at 100yds so it isn’t like I can’t keep it as a HD gun until replaced.

So I think at this point it’s the upper, barrel nut (seems unlikely since I tried two) or barrel and probably just a string of bad barrels. Sound about right?

Oh out of interest, I took off the A2 flash hider. Accuracy seemed to be very fractionally better with it off. But small enough difference to be hard to tell. Some ammo was slightly better with it on, most was slightly worse (the difference between say 4.5MOA and 4.8). One HUGE difference is with it on groups moved about 3” up and 1” right.

I am looking at maybe a Black River Tactical linear comp or KAW linear comp (I am a sucker for the KAW comps and have them on my other ARs). Linear comps seem to be more accuracy neutral from the little I’ve found. Though plenty of comps and brakes don’t seem to impact accuracy much. The better ones are symmetrical brakes and comps (where as the A2 isn’t).

Just curious if anyone has any other suggestions. The barrels are going to go in newer uppers.

First pic is an IMI group and typical of the non-match ammo (and not PMC as it also seemed to do close to the least bad).

The second is an example with what some of the ammo was doing. That one was Frontier 55gr BTHP. Two through one hole, 2 close and 1 far flier (top edge of paper). The Hornady 75gr match was a smaller total group of 5 shots at almost spit on 4MOA (2”), but also a consistent pattern rather than 4 grouped real close and one far off.

Just wondering if some of that odd “3-4 shots close together and the other 1-2 far out” could be a particular symptom of something.

One last question, in checking things, the gas tube DOES touch the gas key as it closes. With the bolt out, it closes under gravity force very easily. But it contacts the gas tube just enough that you can feel a slight vibration in the gas tube as the gas key rides over the gas tube. I can't possibly imagine that would impact accuracy THAT much. There is no binding and it is not slamming in to it.