AR10 not accurate - what to try next?

[Squad51]

I have an AR10 that shoots 2-3 MOA. Aero M5 with 18" .308 Ballistic Advantage barrel with about 250 rounds through it. I know it could be me, but I'm shooting off sandbags and I can shoot much better with other rifles.

I've tried FGMM 175s and I've tried working up handloads in 150 and 168gr. The handloads have all been with IMR4064. I'm considering trying other powders. I have Varget and WIN748 on hand but they are both slower than the 4064. Or I could buy a faster powder (4895?). Or I could put a new barrel in it. Thoughts?

 

[longshot2000]

Well, back up there Sergent. What is your rifle. You say AR-10. That means Armalite? .308 AR rifles are very different, brand by brand. Some are amazing, some are shit.

 

[Squad51]

Well, back up there Sergent. What is your rifle. You say AR-10. That means Armalite? .308 AR rifles are very different, brand by brand. Some are amazing, some are shit.

I was using that term as a generic. Aero M5. Built by a local gun store.

 

[Powder_Burns]

When you say you shoot much better with other rifles, are they also gas guns?
I slapped a 16” .308 together, haven’t shot long guns in 3 years, and grouped under 1” with 168 fgmm. There are a lot of variables to consider here.

 

[Maxduty]

Try the FGMM 168s. Mine loves them.

 

[FCS]

I have an AR10 that shoots 2-3 MOA. Aero M5 with 18" .308 Ballistic Advantage barrel with about 250 rounds through it. I know it could be me, but I'm shooting off sandbags and I can shoot much better with other rifles.

I've tried FGMM 175s and I've tried working up handloads in 150 and 168gr. The handloads have all been with IMR4064. I'm considering trying other powders. I have Varget and WIN748 on hand but they are both slower than the 4064. Or I could buy a faster powder (4895?). Or I could put a new barrel in it. Thoughts?

Buffer weight?
Buffer spring from where?
Gas system length?
Port size?
Brake / flash hider / suppressor adapter?
How much torque on muzzle device?
What buttstock?
What forearm / free float tube?
Adjustable gas block tuned for ejection of brass about 3:30-4 o’clock?

What other rifles are you shooting better? Larger frame AR or -15 in 223 or bolt guns?
Larger frame AR is more demanding, less forgiving of poor technique and follow through.

 

[Punkur67]

I have an aero m5 upper with aero 18" ss barrel and its a decent shooter. I am currently shooting 178gr eldx with varget.

 

[svxwilson]

1. Adjustable gas.
2. Shim or loctite the barrel.

Then try again.

This is what I would suggest trying next. Shims are cheap ($20ish) and loctite 609 or 620 is even lesser expensive and a good adj gas block can be found for around $100.
How familiar are you with shooting large frame ARs? Definitely requires really good technique to get good results as others have mentioned.

 

[smoothy8500]

I've tried working up handloads in 150 and 168gr. The handloads have all been with IMR4064.

It's what I use in my Aero M5-IMR4064 and 168's. You should be at least 1", but as others mention the large frame AR is harder to handle accurately.

 

[beretta682]

Have Somebody else shoot your gun that knows how to shoot a big bore AR then go from there

 

[hlee]

Have Somebody else shoot your gun that knows how to shoot a big bore AR then go from there

The problem is finding someone who actually knows, verses someone who thinks they know...

 

[striped1]

First place I would start is barrel nut torque. Pull the barrel and as some one above said, loctite it or "shim" it. I try to get to the point I have to freeze the barrel and heat the receiver to get them together but loctite will work too. Torque the barrel. I tend to run at the top of the torque specs.

 

[striped1]

also pull the muzzle brake and check the crown.

 

[GUNNER10]

Considering its a mix master its hard to say without seeing the groups, but I would wager that the the barrel might not be torqued properly.

Any chance that your barrel is being contacted by something?

 

[rlsmith1]

Do you guys let the handguard contact the upper receiver or do you leave a small space? When I say small I mean 1mm or so...

 

[drewthebrave]

Do you guys let the handguard contact the upper receiver or do you leave a small space? When I say small I mean 1mm or so...

It depends on the handguard, but in general a small gap is desirable. The barrel nut torque and barrel extension-to-receiver fit is probably more important. However, as others have stated, start with the simple tweaks first:
Remove Muzzle device and inspect barrel crown. Try shooting without muzzle device.
Check optic mount & properly torque screws.
Re-torque barrel nut, bed barrel with Loctite and/or shim with sheet stock to fill large gaps.

Did the seller offer any warranty or guarantees for accuracy? Maybe they can take a look over it for you.

 

[Squad51]

Thank you all for the replies and information. Some more about me and my rifle -
I am more accurate with bolt guns. I've been shooting gas guns for many years, but mostly M16-A2s with iron sights at pop-up targets out to 300m. This is my first large platform AR. The attached photo is typical of the groups I've been getting. The flier in the "4" was me. The other 4 shots were good (at least I thought they were at the time ). I use proper form, breath control, trigger squeeze, etc.

The rifle was way overgassed when I got it. I added a Superlative Arms adjustable gas block and it now ejects at about 3:30. I also added a VG6 brake. Rifle has a carbine length buffer tube with a standard DPMS 308 buffer and spring. It's an M5 with a freefloat handguard that has 8 screws to attach the handguard to the block at the front of the receiver.

I've been running Hdy 168 Match bullets over 41.3-42.0 gr IMR4064, and Hdy 150 FMJBT at 42.0 IMR4064 both in LC brass. I also shoot FGMM factory 175s and the FGMM duplicate handload - 175 SMK over 41.8 IMR4064 in FC brass.

I had to take the rifle back to the store where I bought it several times because it would not chamber rounds reliably. It is running well now. The gun store has gone through several gunsmiths and was recently seeking yet another new 'smith so I don't want to take it back there. It sounds like my next steps are to get 168 FGMM (if I can find some), have a friend who is a good shot test the rifle, and re-torque the barrel.

 

[drewthebrave]

If it's not chambering reliably, then the issue could be with the barrel chamber itself. I'm thinking it may be worth contacting the manufacturer to let them know what you've experienced and start the conversation about a possible replacement.

 

[CrabsandFootball]

This is why you buy a factory rifle from a quality manufacture if you do not have the knowledge and experience to diagnose and maintain your rifle. Even moreso with a large frame AR.

Too many people out there throwing parts together who have no idea how this system works and how parts all made to different specs and tolerances work or don't work together. This includes gun stores throwing crap parts together to move inventory they can't sell.

I would take this back to the store and get a refund due to it not running correctly, and put that money towards a quality factory gun. Your gun store does not have gunsmiths. They have monkeys who can turn a screwdriver. Something anyone on minimum wage with a pulse can do.

 

[sea2summit]

I was using that term as a generic. Aero M5. Built by a local gun store.

Not you? I wouldn’t touch some random gun store’s build. But YMMV.

 

[Squad51]

Too many people out there throwing parts together who have no idea how this system works and how parts all made to different specs and tolerances work or don't work together. This includes gun stores throwing crap parts together to move inventory they can't sell.

You're preaching to the choir. I would certainly do this different if I had it to do over again.

 

[CrabsandFootball]

You may be better off parting the gun out if they won't take it back. Aero let's alot of bad parts through what I assume is qa. At one time they were very good about it as an oem but there are way too many bad receivers out there to reccomend them for a build.

I'm litterly piecing together a LMT mws becuase they A stopped making the gun I want, B parts have become super scarce and C. I know they will work together with minimal dickery. There are way too many junk parts on the market that are designed to remove money from your wallet and they could care less if you get a decent product.

 

[everready073]

Worse case you can contact BA for a new barrel after you rule out other factors. They guarantee MOA

 

[hellishot]

Aero and quality control are not synonymous.

 

[jhutch3313]

Sounds like you are using good ammo, and shooting from bags will help you be more stable, if you are unable to get good groups with the ammo you are using, I would suggest looking at the barrel, if you have the possibility of using a bore scope, or having a gunsmith do it for you. Did you headspace the bolt to the barrel? What kind of bolt are you using? You may try an adjustable carrier to get rid of unwanted gas and recoil. but to me sounds like a barrel issue.