At what point do you give up and rebarrel?

[westford86]

At the end of last year I decided to build a gas gun. I had a ton of fun shooting various semi-auto .308 rifles while stationed overseas and wanted one for myself. I tried not to break the bank, but still went with fairly high quality parts. CMT receiver set, LMT BCG, Geissele trigger, PRI forend and a 16" ADM Heavy contour barrel.

The ADM barrels are all made by Criterion. Criterion even features them on their site. While the barrel was actually less expensive than some of the other options I was considering I put faith in the name and that Criterion wouldn't put out a bad product. I chose this barrel because it was 1/10 twist and 16" with a rifle length gas system, it is also touted to have good things going for it like a M118 LR match chamber and hand lapping prior to finishing.

I was expecting nothing less than 1 MOA (maybe that's unrealistic?) but really I want no less than 3/4 MOA. So far the best I can get the damn thing to shoot is 1.5 MOA. I have tried 175gn and 168gn Federal Gold Medal, Hornady ELD, various other factory ammo, and hand loaded M118LR clones to no success.

Now before you say maybe I just can't shoot, I brought my reliable old Remington 700 5R along with me last time I was at the range an with no other variables changing other than the gun and ammo (I feed it hand loads) I was shooting 5 shot groups at or below .5 MOA.

My last attempt at getting this thing to shoot will be to go heavier with the bullet and see if 190's get the job done, that was sort of my intent with the 1/10 twist and a shorter barrel. However I figured it should at least shoot decently well with standard factory ammo, so that is where I started before investing/dumping time into load development.

Where should I go from here? Try a few more ammo options, or write it off as a lost cause? Send the barrel back and have it checked by ADM/Criterion? As a side note, I am going to be moving across the country soon so I have limited time to waste on a problem rifle, spending limitless range trips to make a reluctant gun shot really isn't in the cards.

Picture, because pictures are better than words...

 

[bfoosh006]

I would suggest checking for odd things... barrel GB to close to the handguard, and possibly bonking the FF tube.... gas tube loose fitting through the upper... GB slightly off the barrels shoulder... all the various scope screws and firearm screws torqued ? ( No offense intended at all , but it does happen.. )

Are you using an Adj. GB ?

Any odd marks on a hand cycled FGMM round ?

How many rounds fired so far ?

And did you try lapping the receiver face flat / true ?

 

[Not_A_Llama]

You should already have punched out and gotten in touch with the manufacturer.

My personal experience is if FGMM or some low-effort handloads don't break the 1 MOA mark, it likely will not be accurate enough to be interesting. I can think of a single exception in almost 20 years of experience.

Maybe a useful datapoint, maybe not: my Fulton/Criterion M110 shoots easily under 3/4MOA 5-shot groups at 100 with FGMM.

 

[westford86]

I would suggest checking for odd things... barrel GB to close to the handguard, and possibly bonking the FF tube.... gas tube loose fitting through the upper... GB slightly off the barrels shoulder... all the various scope screws and firearm screws torqued ? ( No offense intended at all , but it does happen.. )

Are you using an Adj. GB ?

Any odd marks on a hand cycled FGMM round ?

How many rounds fired so far ?

And did you try lapping the receiver face flat / true ?

No offense taken, the first time I brought it to the range and it shot terribly I though it might be something loose, but it's not.

The gas block has plenty of clearance from the handguard, so there is no contact there. It's square and doesn't contact the upper at all. And yes, I am using an adjustable gas block, Superlative Arms.

The brass is coming out looking good. I even used a brass catcher last time at the range to keep them clean for inspection, aside from the usual occasional ding on the mouth of the case with a semi-auto there was nothing visually wrong with the brass. I don't keep track of round count, but if I had to guess I'm at about 150 rounds down the pipe now.

I haven't tried lapping the receiver face, I lack the tools to do so. That being said I've never had to go that far to get desirable results with past AR builds.

You should already have punched out and gotten in touch with the manufacturer.

My personal experience is if FGMM or some low-effort handloads don't break the 1 MOA mark, it likely will not be accurate enough to be interesting. I can think of a single exception in almost 20 years of experience.

Maybe a useful datapoint, maybe not: my Fulton/Criterion M110 shoots easily under 3/4MOA 5-shot groups at 100 with FGMM.

I sort of had a feeling that this barrel might be a dud. FGMM has always been my go-to can this thing shoot well enough to care test ammo.

Since The Fulton and ADM barrels are both coming from the same place I would expect the to shoot with comparable accuracy. If you're getting 3/4 MOA out of yours that makes me very suspicious of my 1.5 MOA results. Out of curiosity, what weight bullet does your Criterion like best? I'm assuming 1-10 twist?

 

[acudaowner]

I would check the gun over but have to realize that your results may not be as good as you want because your skills are not as good as you think or wish them to be . I am not knocking you your gun or your ability . this week end i thought i was doing well at 100 - 500 yards . Only to watch someone who knows how to shoot (shoot the shit out of my guns ) with just a few practice shots and a few adjustments , which made me realize not only have I only just started to learn , but how much more I am in need of learning with every you should have done this or try it this way not like that from behind creteaking eveything i did wrong as he saw it , and my favorite being are your eyes even open . I was not sad by that only inspired to try harder practice slower and learn more . I may never be able to put 4 of 5 shots in one hole @ 100 yards and 3 out of 5 while all still touching at 200 and again at 300 yards , but after seeing what could be done , I sure am going to try harder . Something could be off with your gun it's plausible great gear and ammo can only help , it can't do anything without you having the skills to do it . Nice looking set up btw .

 

[SRPowah]

Gas guns are harder to drive, especially full frame builds... I would toss someone else behind the rifle and verify it is the rifle. The guy who got me into precision shooting sold his .308 AR because he sucked at shooting it, when he can out shoot me on any other weapon system.

 

[Ledzep]

I've fallen into the semi-auto trap before a few times. Most recently I just wanted a .223 P-dog hammer and have chased my fucking tail to no end. Finally on my 2nd barrel on my 2nd upper and 3rd bullet, after finding out I had a bad batch of Winchester brass, I'm consistently shooting 1.25 MOA or better...

Shit's for the birds. From here on out the maximum barrel length is 16.5", and the maximum barrel profile is as thick as will still contain the rifle firing without ballooning, and the maximum optic zoom is 4x in any AR for me. 3rd endeavor (.260 and 6.5 grendel before this) and all end up after way too much money and grief to be on the good side of mediocre. I don't care any more if I could shoot them better or buy better parts. I do not care.

 

[whatsupdoc]

What @SRPowah said.

Before you go nuts have someone shoot the rifle (someone that is a good gas gun shooter).
Ask around if you dont know anyone.

Do you have another gas gun that you are consistent with?

I was looking for a target to post an image but could not find it, anyway.

The target was 10 shots with a 223 gas gun that will shoot .5 moa easy. I was shooting my bolt then picked up the gasser my first 3 shots were 1.5 moa. Im thinking WTF is going on.

I now concentrate on every shot step by step from loading the bi-pod to cheek weld to grip. If it felt uncomfortable I restarted from scratch. The next 7 shots made a .400 inch group nowhere near my first 3 shots.

The gun had nothing to do with the bad groups, it was all due to my sometimes lazy shooting that I get away with with my bolt gun.
The gas gun will punish you if you dont fondle her correctly.

With that all said it could be a bad barrel or not.

 

[Almonz]

Rule out any mechanical errors in the rifle, and then if all is well a re-barrel may be necessary.

 

[hlee]

Bolt guns let you get away with things that gas guns penalize you for. You may be a really good bolt gun shooter, but you may not be that good with the gas gun. I'm not going to try to diagnose what you might be doing wrong, except that blaming the equipment is easy and usually the wrong starting point...

 

[Not_A_Llama]

Since The Fulton and ADM barrels are both coming from the same place I would expect the to shoot with comparable accuracy. If you're getting 3/4 MOA out of yours that makes me very suspicious of my 1.5 MOA results. Out of curiosity, what weight bullet does your Criterion like best? I'm assuming 1-10 twist?

Y'know, oddly, it's an older 1:12, and really loves M118LR or the FGMM 175 and 168s about equally. XBR 8208 + 175 SMKs work stunningly well, too.

1.5 MOA is just not an acceptable barrel. I'd give them a call or email - most manufacturers are very accommodating, as it's better to fix a problem and win praise, rather than have dissatisfied owners out there talking.

 

[Not_A_Llama]

I see guys talking about not being able to shoot semi auto well - I'm actually better shooting gas guns, with hundreds of thousands of reps on AR platforms, than I am bolt guns. When I teach classes, I like to work with my (former) bolt guys to concentrate on followthrough and self-spotting, which tends to resolve problems. People also tend to shoot faster on their semiautos, which increases heat and stringing. Not having to break position at all is a huge advantage that some people "abuse".

I think people also get cheap about their semi-autos; most guys won't think twice about spending $800 on barreling a bolt gun, but get shy about spending $400 on an AR barrel. Maybe it's because the general market is so cheap (I bought a BCA barrel for $42 new this morning). If you have a top rate smith like Paul Craddock spin you up a barrel on something like a Bartlein blank, and feed quality ammo, you're gonna have a very very good time.

 

[RTH1800]

Did you indicate the GB should be off the shoulder or butted up to it? I have read both.

 

[westford86]

I see guys talking about not being able to shoot semi auto well - I'm actually better shooting gas guns, with hundreds of thousands of reps on AR platforms, than I am bolt guns. When I teach classes, I like to work with my (former) bolt guys to concentrate on followthrough and self-spotting, which tends to resolve problems. People also tend to shoot faster on their semiautos, which increases heat and stringing. Not having to break position at all is a huge advantage that some people "abuse".

I think people also get cheap about their semi-autos; most guys won't think twice about spending $800 on barreling a bolt gun, but get shy about spending $400 on an AR barrel. Maybe it's because the general market is so cheap (I bought a BCA barrel for $42 new this morning). If you have a top rate smith like Paul Craddock spin you up a barrel on something like a Bartlein blank, and feed quality ammo, you're gonna have a very very good time.

Funny you mention Craddock, I just got off the phone with someone there. My 300 blackout is Craddock, not that accuracy matters much for 300 blackout, but the barrel is a beauty! I had originally contacted him about about getting a barrel for the .308 build in question in this thread. A friend of mine got his .308 barrel from Craddock and it's been fantastic, pretty much shoots sub-moa with anything you feed it. I stupidly backed out of getting a Craddock because I just didn't want to spend the extra $200-$300 to get exactly what I wanted with a Bartlein tube, the ADM/Criterion was ready to ship and in the length I wanted with a rifle gas system. When I told the person at Craddock about the results I was getting with my curent barrel they were shocked as Craddock does a lot with Criterion blanks and always has good results. I need to email Paul, if they aren't too backed up with orders I might decide to rebarrel. They also said I could send in my bolt for headspacing for no extra charge.

As for gas guns vs. bolt guns, I don't want to seem arrogant but I have no issues shooting a semi-auto. I know how easily things can devolve into a petty flame war on the internet while proving my worthiness to strangers, so I am refraining from engaging on that front. I have put way more rounds down range on a semi-auto than a bolt gun, I in fact only own one functioning bolt gun; also my personal record for distance is with a semi-auto, albeit something not of the AR family. I guess I worded my original post poorly and might have given people the impression I have never shot a semi-auto before, I have just never personally owned a .308 AR before. Of my two previous 5.56 AR precision rifles I never had any issues getting them to shoot sub-moa in the prone off a bi-pod, let alone in a rest on a bench. Again, not trying to sound arrogant, but getting any rifle capable of shooting sub-moa to group well at only 100 meters is easy. I know it's easy to blame the shooter, but after a lifetime of shooting I'm pretty sure my inability to operate a gas gun would have surfaced much earlier.

 

[westford86]

What @SRPowah said.

Before you go nuts have someone shoot the rifle (someone that is a good gas gun shooter).
Ask around if you dont know anyone.

Do you have another gas gun that you are consistent with?

I was looking for a target to post an image but could not find it, anyway.

The target was 10 shots with a 223 gas gun that will shoot .5 moa easy. I was shooting my bolt then picked up the gasser my first 3 shots were 1.5 moa. Im thinking WTF is going on.

I now concentrate on every shot step by step from loading the bi-pod to cheek weld to grip. If it felt uncomfortable I restarted from scratch. The next 7 shots made a .400 inch group nowhere near my first 3 shots.

The gun had nothing to do with the bad groups, it was all due to my sometimes lazy shooting that I get away with with my bolt gun.
The gas gun will punish you if you dont fondle her correctly.

With that all said it could be a bad barrel or not.

I don't currently own another precision gas gun. I sold my 5.56 Noveske to finance this build; that gun however was a 3/4 MOA shooter all day with factory ammo.

I've owned some form of an accurate semi-auto for at least ten years now and never had issues shooting them. I don't discredit the fact that any shooter can have an off day, but I haven't ever really struggles to make rifles, semi-auto or bolt, shoot well if the conditions permit. The first time I brought this particular .308 to the range I thought that maybe I had forgotten how to shoot, but when it was still shooting like shit on the second and third time out, shooting off bi-pod and off a rest in ideal conditions with various quality ammo, that is when I really started to doubt it. That's why I dusted off my bolt gun just to make sure I hadn't lost my mind and could still hit the side of a barn.

 

[westford86]

Did you indicate the GB should be off the shoulder or butted up to it? I have read both.

I am also unclear as to what is best regarding the gap. I think that the gap between the gas block and the shoulder might be a carry over from old milspec rifles when you had to account for the handguard endplate.

From what I've read the only time the gap, or lack of, might matter is in terms of functionality and getting the gas port lined up. I am not tracking that it has much effect on accuracy, but that could be something I am just ignorant of.

 

[RTH1800]

West,
Thanks. I get similar conflicting reports. I do know that MIL SPEC is .015 off the shoulder IIRC most likely due to gas port alignment.
I still butt mine in contact and adj the gas block.

 

[Not_A_Llama]

I have never seen a gas block with a port small enough to make the gap matter. Most predimpled barrels I’m seeing today measure in a way that suggests barrel manufacturers don’t consider the gap anymore.

Frankly, with as overgassed as most barrels come today, a little occlusion would do most rigs some good.

 

[palmettoman]

I have 2 Criterion barrels in bolt rifles that are fantastic. None of their gas varieties, however.

I had the same type issue with my AR10 in 6.5 CM. I lapped the receiver, glued the barrel, made sure everything was right with the gas tube, etc., but the rifle would never group consistently. It would throw a shot in virtually every group. My loads were good, so it wasn't the ammo. I finally gave up and ordered a new barrel. Just installed it over the weekend and will try it out for the first time Monday. I should have done it long ago.

I'd send it to them for a check-up. It won't hurt and will give you peace of mind either way it turns out.

 

[westford86]

I'd send it to them for a check-up. It won't hurt and will give you peace of mind either way it turns out.

Yup, Criterion is helping me out. The upper is already on the way to them. Luckily their customer service is very accommodating and willing to take time to help out customers.

 

[Jsp556]

Melonite treated barrel? Scope the throat. A shitty chamber job that’s been melonited isn’t going to shoot well.

 

[Campguy308]

I have a custom barrel rig that I've spent a lot of money on that was chambered by a well known reputable company. 6.5x47 lapua. It wouldn't shoot for shit. Sent it back to them and they said it was full of copper. They said they cleaned it out and shot it until it stopped loading up with copper, and said it's hammering now. We will see when I get it back. I have limited patience for poor shooting barrels. Let us know how it goes

 

[westford86]

I will certainly post about the outcome once I get the barrel back from Criterion. They have a theory on what's going on, but I am going to wait until I have conclusive information to say anything. It'll be at least two weeks as I've got a block of training starting Wednesday, so no time to fuss around with gun stuff.

These rifles were all built with the best technique (digital torque wrenches and gas block alignment jigs and lapped receivers and and and).

What tools do you use for lapping the receiver? I think it's time in invested in that.

 

[Eoddave27]

As others have already said a gas gun and a bolt gun are two different animals to shoot. It took me awhile to figure that out. Two things that I have had issues with though are the gas block hitting the handguard and not lapping the receiver and bedding the barrel. If you look at criterion’s installation instructions I believe that is specifically mentioned. A lot of people think lapping and bedding are not important but it made a huge difference for my rifles.

 

[8208]

Check the fit of barrel extension in the receiver. It should be snug with no slop. If it has slop, shim it or use loctite around it and let it settle. verify that the gas block isn't hitting and is tight. Trace the gas tube back and verify it isn't touching anywhere either. This is going to sound dumb but verify your scope rings or sights are torqued. I have seen many people so excited with a new rifle that forget to tighten the scope down past hand tight. If none of that applies, your only option would be to re-barrel. I would go with krieger or bartlein if you can swing it. AR's are dime a dozen... invest in good barrel and a good trigger and the work is usually done.

 

[westford86]

For all the people who insisted it was me and not the gun I am happy to say it was indeed the gun. I had Craddock Precision turn a new barrel for me, 18" Rock Creek cut 5R 11.25 twist. I also got a new bolt, headspaced to the barrel by Paul.

After sending some rounds to get the gas system tuned I ran a couple patches down the barrel, shot a group with some Federal Gold Medal, zeroed, then shot another group and one more after that with Hornady ELD. All three groups were about 3/4 MOA.

I really want to get this thing down to 1/2 MOA, and I think that will be possible with the development of a good hand load; I was also not shooting very well the other day (plus some other environmental excuses) so there is probably plenty of room for improvement on my end as well.

I should also mention that some 178gn Hornady ELD I ran through the gun later were still about 3/4 MOA, but blowing out primers! I immediately stopped shooting that ammo once I noticed; it also quickly explained why I was having functional issues with that batch if ammo. I've never had "premium" factory ammo blow primers before, has anyone else had that issue with ELD?

 

[r.tenorio671]

..reference your 178gn Hornady experience, when you tuned your gas block was it with the Hornady ammo? I run a SLR AGB on my .308 gasser with a 16" BA Hanson and tune it to the ammo that will be used the most. I found that with the heavier bullets (handloads and factory both) my "normal" setting for 155gn HDY OTM bullets or generic 147gn M80 type ammo will have MORE pressure generated with the heavier bullets, i.e. 168 HDY OTM, 178gn HDY OTM and FGGM 168 factory.