AR15 accuracy issues

A

adaw28

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Minuteman
Nov 28, 2019
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10
#1
Hi everyone, I'm looking for advice on an AR15 that I can't get to shoot. It's about 1.25-3MOA and very inconsistent. It's chambered in 6 ARC and it's a home build. I'm also not claiming to be an expert shooter but I've built 3 other AR15s and one AR10 that all shoot less than 1 MOA.

The rifle in question originally had a Shaw barrel and had the same issues. I tried disassembling and reassembling making sure everything was torqued correctly etc. I finally replaced the barrel with a Proof stainless barrel but I'm still having finicky results. I've got about 60-80 rounds on the new barrel.

Any suggestions on what I should check next? It does seem to have a little bit more vertical dispersion than horizontal so I'm almost wondering if it could be something in the handguard, barrel nut upper receiver chain. I have tried to put consistent pressure on the bipod, so off that's the issue, then this gun is far more sensitive than any other I have.

Other parts are BCM stripped upper receiver. Alexander arms bolt, Areo precision handguard. Aero lower parts kit, aero adjustable gas block, geissele SSA-e trigger, and Primary arms 4-14 R-Grid scope.
 
#2
Could be a lot of things, but check the inside of your Aero handguard to make sure you aren't able to apply pressure to the barrel and get your gas block to touch. Those ATLAS handguards can pretty easily make contact if you are running a barrel that has a gas block larger than .750".

Again it could be a lot if things, but I once fought a situation like yours and finally figured it out after swapping two barrels. Same thing can happen if you let your M-LOK T-slot nuts make contact with the barrel too.
 
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#3
Once I seen 6 arc I was like, that’s why. It really, 6 arc in gas guns can be tough. What ammo are you using, factory or your own loads?
 
#4
I’d suspect something deflecting the barrel or your scope/red dot/optic, as indicated above. Or maybe something off with the barrel nut…rare, but possible. Is there any free play at all in the barrel after torquing it down? Check fore/aft as well as side-to-side, and up/down.

And BCM’s pretty good, I have a couple of their uppers, but it wouldn’t hurt to confirm the upper is square too.

Buy or borrow a lead sled or similar, or at least remove the bipod temporarily and use bags or something from a bench rest to remove one of the variables.
 
#8
Separate the upper and lower remove the charging handle slide the bolt carrier in and out and look for gas tube movement. If the tube is moving it's not aligned correctly.

If you have a muzzle device remove and shoot without it.

As others have mentioned try a known good scope.

If you have access to another bolt try that Proof barrels are headspaced with JP bolts.

What's your barrel nut TQ?
 
#9
Ernest 5.56 said:
Separate the upper and lower remove the charging handle slide the bolt carrier in and out and look for gas tube movement. If the tube is moving it's not aligned correctly.

If you have a muzzle device remove and shoot without it.

As others have mentioned try a known good scope.

If you have access to another bolt try that Proof barrels are headspaced with JP bolts.

What's your barrel nut TQ?
Click to expand...
The first time with the proof barrel I think I torqued it to 40 ft/lbs. When I reassembled I tried going up to either 45 or 50 just to see if that would change anything.

I don't have another bolt but that might be something I try if nothing I can do otherwise works.
 
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#10
adaw28 said:
The first time with the proof barrel I think I torqued it to 40 ft/lbs. When I reassembled I tried going up to either 45 or 50 just to see if that would change anything.

I don't have another bolt but that might be something I try if nothing I can do otherwise works.
Click to expand...

You can also take a round and chamber it from left and right and see if the jacket or tip is getting damaged on feed ramps etc
 
#13
diggler1833 said:
Could be a lot of things, but check the inside of your Aero handguard to make sure you aren't able to apply pressure to the barrel and get your gas block to touch. Those ATLAS handguards can pretty easily make contact if you are running a barrel that has a gas block larger than .750".

Again it could be a lot if things, but I once fought a situation like yours and finally figured it out after swapping two barrels. Same thing can happen if you let your M-LOK T-slot nuts make contact with the barrel too.
Click to expand...
I'll second this post. Any part on the barrel bonking the handguard can cause odd results.

And I'd try the bags ( as mentioned ) instead of the bipod.
 
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#14
Ernest 5.56 said:
Separate the upper and lower remove the charging handle slide the bolt carrier in and out and look for gas tube movement. If the tube is moving it's not aligned correctly.

If you have a muzzle device remove and shoot without it.

As others have mentioned try a known good scope.

If you have access to another bolt try that Proof barrels are headspaced with JP bolts.

What's your barrel nut TQ?
Click to expand...
I tried this and it pushes the gas tube ever so slightly up.
bfoosh006 said:
I'll second this post. Any part on the barrel bonking the handguard can cause odd results.

And I'd try the bags ( as mentioned ) instead of the bipod.
Click to expand...
I'll try bags instead of the bipod. Nothing was contacting the barrel. Double checked as I was loading the bipod (took some creativity to do by myself..)

Anyone who has changed a barrel bedded with loctite, do you need to clean/lap the receiver and or barrel extension before putting it back in? Or just apply more loctite and go?
 
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#15
Loctite on a barrel nut ?

I use antisieze and torque it down.

Or you talking about liquid shim type thing that is basically plastic.
 
Last edited:
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#17
Got it.

I have read about that and can't remember the loctite # used for that but if you know they should have removal procedures online.

Mine have all fit tight enough I never considered it.
Some had to go in the freezer to get assembled.

Lucky?
 
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#18
Snuby642 said:
Got it.

I have read about that and can't remember the loctite # used for that but if you know they should have removal procedures online.

Mine have all fit tight enough I never considered it.
Some had to go in the fridge to get assembled.

Lucky?
Click to expand...
I think I saw it in a video by criterion barrels years ago. 620 is the # but I don't remember seeing anything about removing it. I'll see what I can find.
 
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#21
adaw28 said:
I tried this and it pushes the gas tube ever so slightly up.

I'll try bags instead of the bipod. Nothing was contacting the barrel. Double checked as I was loading the bipod (took some creativity to do by myself..)

Anyone who has changed a barrel bedded with loctite, do you need to clean/lap the receiver and or barrel extension before putting it back in? Or just apply more loctite and go?
Click to expand...
Just clean and go, here is a little demo.

Removing Loctited AR barrel

 
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#22
I wouldn’t loctite the barrel until you pinpoint what’s making it shoot so poorly.

I’d swap the barrel over to one of the uppers that’s a known shooter, make sure the gas block isn’t contacting the inside of the forend, and head to the range with that setup and a spare optic. That way you can test whether it’s the receiver, barrel, or optic or eliminate all of them as the culprit.
 
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#23
Just because the OP has a home built 6 ARC gas gun doesn't mean it will not shoot factory ammo sub moa. Here's a pic of some of the first shots from my home build in 6 ARC shooting factory Hornady 108 ELD-M ammo while I was dialing in the scope zero. I'm using an X-Caliber barrel and JP full mass bcg.

It's already been mentioned, but I would check the gas key and gas tube alignment. Do this by hand with the bolt out of the bolt carrier and slide the bolt carrier into "battery" so you can watch for movement of the gas tube when it engages with the gas key. It should slide in without any (or nearly any) movement. Also it's been mentioned already, but I would also check for the gas block to handguard fitment and be sure it's got plenty of room. Lastly, it could be the barrel isn't the best since it's Shaw.

6mm_ARC_Rifle_First-Shots.jpg
 
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#24
stevieb92 said:
Just because the OP has a home built 6 ARC gas gun doesn't mean it will not shoot factory ammo sub moa. Here's a pic of some of the first shots from my home build in 6 ARC shooting factory Hornady 108 ELD-M ammo while I was dialing in the scope zero. I'm using an X-Caliber barrel and JP full mass bcg.

It's already been mentioned, but I would check the gas key and gas tube alignment. Do this by hand with the bolt out of the bolt carrier and slide the bolt carrier into "battery" so you can watch for movement of the gas tube when it engages with the gas key. It should slide in without any (or nearly any) movement. Also it's been mentioned already, but I would also check for the gas block to handguard fitment and be sure it's got plenty of room. Lastly, it could be the barrel isn't the best since it's Shaw.

View attachment 8288105
Click to expand...
It doesn’t mean it won’t, but doesn’t mean it will either. Yours seems like it was off to a good start, good shooting.
 
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#25
Cfshooter said:
It doesn’t mean it won’t, but doesn’t mean it will either. Yours seems like it was off to a good start, good shooting.
Click to expand...

Agreed. The same can be said for a factory off the shelf rifle. The fact that it was home built has no relevance on whether or not it will shoot well, so it wasn't a worthwhile response to be brought up.
 
#26
stevieb92 said:
Agreed. The same can be said for a factory off the shelf rifle. The fact that it was home built has no relevance on whether or not it will shoot well, so it wasn't a worthwhile response to be brought up.
Click to expand...
So true, I didn’t even weigh in the fact of it being a home build, to me it is more about the barrel and bullets/components/shooter. I am not even sure you can buy a factory gas gun that shoots as good or better than a quality barreled home build. Well, maybe a few “factory” built that use cut rifle barrels will do.
 
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#27
stevieb92 said:
Just because the OP has a home built 6 ARC gas gun doesn't mean it will not shoot factory ammo sub moa. Here's a pic of some of the first shots from my home build in 6 ARC shooting factory Hornady 108 ELD-M ammo while I was dialing in the scope zero. I'm using an X-Caliber barrel and JP full mass bcg.

It's already been mentioned, but I would check the gas key and gas tube alignment. Do this by hand with the bolt out of the bolt carrier and slide the bolt carrier into "battery" so you can watch for movement of the gas tube when it engages with the gas key. It should slide in without any (or nearly any) movement. Also it's been mentioned already, but I would also check for the gas block to handguard fitment and be sure it's got plenty of room. Lastly, it could be the barrel isn't the best since it's Shaw.

View attachment 8288105
Click to expand...
Shaw was the first barrel. When I couldn't get it to shoot I finally replaced with a Proof SS. Still can't get it to shoot so I'm thinking it's not the barrel.
 
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#28
adaw28 said:
Shaw was the first barrel. When I couldn't get it to shoot I finally replaced with a Proof SS. Still can't get it to shoot so I'm thinking it's not the barrel.
Click to expand...
Since you seem to have done most of the trouble shooting, I would try and develop a load for it if you reload, if you do not, try different ammo. I still am leaning towards barrel.

Take a poll on how many people have gas 6arcs that shoot sub moa consistently with factory ammo. Shooting consistent moa with any caliber in a gas gun with factory ammo isn’t always easy.
 
#32
I really think it's the hornady ammo.
All 3 types he shot are secant ogive. They are pretty jump intolerant IMHO.

They will fly great when you get them dialed in perfectly, harder to do in a gasser.

I looked around and could not find any other factory rounds that didn't have the same bullets, disappointed.

If you can't reload I would suggest looking into getting an EC Tuner Brake.
That may be able to tune the factory rounds in.

Not that long ago I could not get brass for my 6.5 grendel.
Ended up with Hornady and another manufacturers rounds and both were 1 1/2 moa at best.
 
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#33
Factory Hornady 108 ELDM shoot just fine out of two 20" Proof Carbon barrels. Mine holds around .6-.75 at 100. My buddy's is around .75-1" with him shooting. He tried the 105 BTHP loads and it was about the same. Based on what I have seen I doubt its the ammo.

Speed has been around 2660 with an SD of 13. Not too bad for factory ammo in my rifle. During break in it was around 2640.
 
#34
Snuby642 said:
I really think it's the hornady ammo.
All 3 types he shot are secant ogive. They are pretty jump intolerant IMHO.

They will fly great when you get them dialed in perfectly, harder to do in a gasser.

I looked around and could not find any other factory rounds that didn't have the same bullets, disappointed.

If you can't reload I would suggest looking into getting an EC Tuner Brake.
That may be able to tune the factory rounds in.

Not that long ago I could not get brass for my 6.5 grendel.
Ended up with Hornady and another manufacturers rounds and both were 1 1/2 moa at best.
Click to expand...

My best guess is the bolt but who is to say it's not something in the lower
 
#36
adaw28 said:
I'm thinking about getting a JP bolt but want to try to eliminate all other variables before spending the money. Can you elaborate on the lower? I thought of all things it would have the least affect..
Click to expand...
It would be from the fire control group low hammer speed causing inconsistent ignition.

Probably not the issue but easy to test and rule out....
 
#37
Snuby642 said:
I really think it's the hornady ammo.
All 3 types he shot are secant ogive. They are pretty jump intolerant IMHO.

They will fly great when you get them dialed in perfectly, harder to do in a gasser.

I looked around and could not find any other factory rounds that didn't have the same bullets, disappointed.

If you can't reload I would suggest looking into getting an EC Tuner Brake.
That may be able to tune the factory rounds in.

Not that long ago I could not get brass for my 6.5 grendel.
Ended up with Hornady and another manufacturers rounds and both were 1 1/2 moa at best.
Click to expand...
Could be. I'm not really sure. I am set up to reload, but I'm really just getting into it. I'm not sure I'm really confident in my ability to work up a good load yet.. Plus I'd still rather have a rifle that shoots factory remote good if possible.
 
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#38
If the accuracy swing is really 1.25-3moa, it’s got to be some sort of interference that’s breeding inconsistency. I just don’t see 3 different bullets all being dogshit and inconsistent.

I’d be looking at the gas system, handguard or bolt like others have said.
 
#39
There are a cabillion people on the hide that will help you get a load for that ar going.

Pretty much the brass needs to fit and be bumped back 2-4 thousands, I do 2 and I do 2 thousands for neck tension.

Some people have allready mentioned thier loads work powder up and keep checking it for damage.

The secant ogive bullets are picky as to seating depth as apposed to tangent ogive bullets but we know they are a long range favorite.

I would advise against trying to parts swap and spend my way out of this without custom loads first.
 
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#40
adaw28 said:
Could be. I'm not really sure. I am set up to reload, but I'm really just getting into it. I'm not sure I'm really confident in my ability to work up a good load yet.. Plus I'd still rather have a rifle that shoots factory remote good if possible.
Click to expand...
What better time to start than now? I think that is how you will get the most out of that pipe.
 
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#41
adaw28 said:
I'm thinking about getting a JP bolt but want to try to eliminate all other variables before spending the money. Can you elaborate on the lower? I thought of all things it would have the least affect..
Click to expand...

Go ahead and get the bolt anyway, worst case scenario you'll have a spare.
 
#42
adaw28 said:
Factory Hornady ammo for now. I've run the 103 eldx, 105 bthp, and 108 eldm.
Click to expand...
This is most-likely your problem... Hornady ammo has never shot worth a damn in either of my 6.5 Grendel barrels, and it wouldn't shoot worth a shit in my bolt-action 6 ARC either. My $0.02 is to try some handloads, or find some better factory ammo.

My 6.5 Grendel shot 2 MOA with factory Hornady ammo, and after handloading, the same barrel puts down 1/3 MOA groups.
 
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#44
Thanks everyone for the input. I'm not going to have time to work on it for a while here, but I've got a spare BCM upper I can swap, reassemble. I'm going to check the gas tube/key alignment, and swap in a scope/mount I know shoots well.

If that doesn't do it, I'm thinking next step would be getting a JP bolt, or reloading. Unless there is a way I can check if headspace is an issue by measuring? How would one do that? Just go/no go gauges? Measuring fired brass?
 
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#45
adaw28 said:
Thanks everyone for the input. I'm not going to have time to work on it for a while here, but I've got a spare BCM upper I can swap, reassemble. I'm going to check the gas tube/key alignment, and swap in a scope/mount I know shoots well.

If that doesn't do it, I'm thinking next step would be getting a JP bolt, or reloading. Unless there is a way I can check if headspace is an issue by measuring? How would one do that? Just go/no go gauges? Measuring fired brass?
Click to expand...

I looked for loaded ammo only found hornady and HSM.

I thought someone else would be making loaded ammo by now

Edit looks like copper creek makes ammo

Copper creek 6arc
 
#46
Measure fired brass should do.

All our 223 barrels are +/- 0.0005 thousands . I so I can use the same brass in all of them, 7 total.

They are all right down on top of a go gauge and I expect yours will be right there as well.

I had one ar that was out by
0.002 got a new bolt and gtg
 
#47
adaw28 said:
Unless there is a way I can check if headspace is an issue by measuring? How would one do that? Just go/no go gauges? Measuring fired brass?
Click to expand...
Your fired brass will let you know your headspace.

The thing with factory ammo is there is usualy a lot of space your round is rattling around in.

www.hornady.com

Lock-N-Load® Headspace Comparator & Anvil Base Kit - Hornady Manufacturing, Inc

Lock-N-Load® Headspace Comparator & Anvil Base Kit Lock-N-Load® Headspace Comparator The Lock-N-Load® Headspace Comparator extends brass life, improves accuracy, and enhances safety. The gauge measures...
www.hornady.com www.hornady.com
 
Last edited:
#48
adaw28 said:
Thanks everyone for the input. I'm not going to have time to work on it for a while here, but I've got a spare BCM upper I can swap, reassemble. I'm going to check the gas tube/key alignment, and swap in a scope/mount I know shoots well.

If that doesn't do it, I'm thinking next step would be getting a JP bolt, or reloading. Unless there is a way I can check if headspace is an issue by measuring? How would one do that? Just go/no go gauges? Measuring fired brass?
Click to expand...
Just start reloading now, that will get that barrel shooting the best of its capabilities.

I’m willing to bet all that other stuff doesn’t do any different.
 
#49
Snuby642 said:
Your fired brass will let you know your headspace.

The thing with factory ammo is there is usualy a lot of space your round is rattling around in.

www.hornady.com

Lock-N-Load® Headspace Comparator & Anvil Base Kit - Hornady Manufacturing, Inc

Lock-N-Load® Headspace Comparator & Anvil Base Kit Lock-N-Load® Headspace Comparator The Lock-N-Load® Headspace Comparator extends brass life, improves accuracy, and enhances safety. The gauge measures...
www.hornady.com www.hornady.com
Click to expand...
I've just been accumulating brass for the time being, figured I'd get the barrel broke in with factory ammo, but it should be to that point by now. I have tried prepping some of the brass and I'm getting some inconsistent head space numbers after full length sizing. I'm not sure if it's something with the sizing or measurement.. like +/- 2 thou
 
#50
Something loose?
Too much lube on case?

I deprime separately in a universal die then tumble to clean.

I polish down the expanding button to 0.004 under bore till mirror finish it sizes smoothly and always lube inside case mouth dry or wax.

Then it gets the 0.002 mandrell. The shoulder is pretty rock steady.

I found one thing out with the 69g rounds today is the base to ogive is varying, crap.

Guess I need a better seating die.
 
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