Tips for running a large frame gasser?

[quiksilverj]

Hello all,

I have picked up a 308 gas gun and it has been a pretty good love hate relationship for us. Some days she performs well and others not so much in the accuracy department. This last weekend I said screw it and shelved the 6.5 creed bolt gun which solidly produces .5moa groups and does very well at extended ranges and shot the gasser. On some of the positional stages she surprised me and held her own on some pretty small targets so I was starting to like her again. At 960 on a full size ipsc she was all over the place and we argued like usual. Thus the roller coaster we have been on. If I shoot groups at 100 yds she will sometime dump them into about a .75 MOA group but is usually in the 1.5 ish range. I am not sure if I am expecting too much from the weapon system or not (this is my first large frame). I do have a ar-15 I built with a WOA barrel that shoots very well and has sold at least 6-7 more barrels based on its performance. I also realize I have mentioned 3 different animals here ar-15, bolt gun and the large frame. I can tell that the large frame is unlike the others just from the recoil impulse. It feels way different on the recoil impulse and compared to the small frame it feels like it takes 10 times longer.

So my question to the forum here is what advice can you give me to run this monster better? Assume all I have ever shot is a bolt gun and what should I do differently to ring the most out of the gasser. Is it unreasonable to expect under an MOA from this system which is from a very reputable builder? (I did not build it myself but would prefer to not mention the maker as I think the problem is most likely me)

Rifle - 18 in barrel 1 in 10 twist with an intermediate gas system. Unsuppressed. Geiselle NM DMR trigger.

Ammo - I have tried the following 168 fgmm, 175 fgmm, federal premium with 185 juggernauts (shot the match with these), handloaded a load workup with 175 smk and 178 hornady hpbt. Results were roughly the same with everything. Sometimes good groups less than a moa but never 2 in a row under an moa. Average is in the 1.5 to 1.75 moa

 

[Fursniper]

The obvious 1st question is what kind of ammo are you running? Factory or handloads. Details.

 

[quiksilverj]

Good catch my bad. I will update the original post as well.

Rifle - 18 in barrel 1 in 10 twist with an intermediate gas system. Unsuppressed. Geiselle NM DMR trigger.

Ammo - I have tried the following 168 fgmm, 175 fgmm, federal premium with 185 juggernauts (shot the match with these), handloaded a load workup with 175 smk and 178 hornady hpbt. Results were roughly the same with everything. Sometimes good groups less than a moa but never 2 in a row under an moa. Average is in the 1.5 to 1.75 moa



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[Fursniper]

Looks like all the ammo you're using is good stuff. As its all producing the exact same results, my gut tells me it's the barrel, I mean any gun no matter the builder, if it's has a mediocre or worse barrel is not going to shoot well. Even a good barrel manufacturer knocks out a poor barrel occasionally. It's being consistant but consistantly poor. You didn't mention round count but I'm assuming it's not shot out. My AR 10 is also very consistent but consistently good (sub moa). Since you are getting consistently good 1/2" groups with you bolt gun, again, I would give you the benefit of the doubt and again, say it's a poor barrel. If you were a lousy shooter you'd be getting poor results with the 6.5 too I think. If you want to confirm that, have someone else that's a decent shooter have a go with the gasser, if they get the same results it's a pretty good bet it's time to swap barrels. On the other hand, if they're getting 1/2" groups, it's time to improve your form with the AR! That's where I'd start anyway.

 

[Forward543]

I am in the same boat currently. But i think you need better accuracy. I dropped my .308 barrel for a 24" 6.5 cm. Im getting about .5-.75 moa out of it. I like it better for time on stages, but the recoil is higher. I went to a jp lmos carrier with hp bolt and that helps. The other thing is i strap my game changer to the hanguard, and that helps. My gun is too light as it has a christensen carbon barrel. I say make it heavy, go to a 6.5 or 6mm, and brake the hell out of it. Recoil to see my shot placement seems to be my current issue. But you should be able to get better accuracy with a gas gun.

 

[lizzardking308]

Are your groups 3 or 5 shots? While I don't know you at all, from my experience, both personally and from watching others, a large frame AR will exploit any errors in your form, from natural point of aim through trigger pull and follow through. I would say if your rifle will do 0.75 MOA 5 shot groups, but then they open up for the next group, it could be you're slacking off in your form some. The large frame AR's love to show you in no uncertain terms that you made a mistake in form when you lose focus and make you look silly. Personally, I would focus more on the Indian and not the arrow as anytime I am feeling cocky I bust out a semi 308 and humility is not far around the corner, especially if the wind is blowing. Just my $0.01. Best of luck!

 

[ZombieMonkey]

Are your groups 3 or 5 shots? While I don't know you at all, from my experience, both personally and from watching others, a large frame AR will exploit any errors in your form, from natural point of aim through trigger pull and follow through. I would say if your rifle will do 0.75 MOA 5 shot groups, but then they open up for the next group, it could be you're slacking off in your form some. The large frame AR's love to show you in no uncertain terms that you made a mistake in form when you lose focus and make you look silly. Personally, I would focus more on the Indian and not the arrow as anytime I am feeling cocky I bust out a semi 308 and humility is not far around the corner, especially if the wind is blowing. Just my $0.01. Best of luck!

^^^This! A bolt gun is significantly easier to shoot well as is a AR15. Once you step up to the large frame guns they will definitely reveal shooter errors that may have previously been unnoticed. Just keep shooting.

 

[quiksilverj]

Thanks for the advice guys. It's a new barrel on it with about 300 rounds on it I'd say. I do believe that it is me with the differences between a gas gun and a bolt gun. What I am wondering is do you guys incorporate different technique with a gas gun? Do you usually try to torque the gun to take up slack between the upper and lower? heavily load it into your shoulder or medium? Just looking to see if there is any consensus you guys have seen to affect accuracy in addition to the fundamentals.

 

[lizzardking308]

Speaking from what works for me, torque is bad, relaxed is good. Muscle tension can change as the trigger breaks and you are impacted by the three recoil impulses. I focus on natural point of aim, seating the rifle in my shoulder pocket, a good trigger pull (don't release until after spotting impact) and following through. For me it's 90% mental focus with a gas gun. I can't be lazy and expect good things to happen. That's what makes my MWS one of my favorite rifles as it keeps me honest. The best advice is to shoot it. A lot. Burn some powder and get comfortable with the rifle. I have seen friends flinch on a bolt gun and get away with it. Same occurrence with my LMT is usually tragic.

 

[mkollman74]

Well, not all large frame ARs are created equal. Assuming you have a quality setup, I would suggest two things that have helped me: be sure you understand the load your bipod likes, and be OCD with follow through on your trigger pull. Also, the temptation is often to grip the hell out of the pistol. grip, try a "thumbless" grip on for size.

 

[Black max]

+1 on the thumbless grip. Also be sure your trigger finger is perpendicular to the trigger and pull straight back. I know it seems simple but lock time is a bitch! Small movements between release and ignition = shit results down range.

 

[deersniper]

The online training covers running a semi in detail. It made a big difference for me.

 

[Rthur]

Are these groups ending with an empty mag?
The difference in recoil on the last round can open the groups up.
Also, don't let up on the trigger, after the break, until the recoil impulse is over.
Then just enough to trip the trigger reset.
Exaggerate your follow through.

R

 

[winniedonkey]

Where is your thumb while shooting?

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[quiksilverj]

I was hoping to get out to the range today but no luck since we took advantage off the sale on mulch at Lowes. Landscaping is better than shooting right? Anyway to answer a few of the questions when shooting groups I am a firmly in the 5 shots camp. I very much focus on the tempo of fire a round and after the rifle cycles I want to hear the click of the trigger reset. Usually I do wrap my thumb but will give it a go without it next time out. I just got an HDMRii in the mail on Friday and mounted it up last night so I will have a little more power for the group shooting now. I don’t think this will change much since I had a pretty proven SWFA 3-15 on it for a while till this became available. Next rang trip with it I plan to just hammer shots down range and figure out what it likes with different techniques and just try to troubleshoot the rifle to see if there is anything amiss. Thanks for the responses and I’ll report back how it goes.

 

[K-tech]

Hello all,

I have picked up a 308 gas gun and it has been a pretty good love hate relationship for us. Some days she performs well and others not so much...

DID YOU JUST ASSUME YOUR RIFLE'S GENDER??? Jk but have you tried letting another competent person shoot it? If they keep getting the same results it's probably the rifle

 

[L.R.Novice]

What stock do you have and is there play between it and the rifle?

 

[agbm]

By chance are you running a muzzle brake or suppressor? Recoil is 2 fold with a gas gun, you could also try a recoil buffer: https://www.kyntec.com/shop/

 

[kingzero]

I was in the same boat as you with my 308. I was frustrated as hell when I first got it due to inconsistent groups. It would go from 1.5 MOA groups to .5 MOA groups all the time. I finally worked up a routine for shooting it that consists of getting square behind the rifle, getting the bipod height right, getting the stock firmly into the pocket, hand placement on the grip, finger placement on the trigger, loading the bipod and most important follow through. If I get sloppy it will kick my ass and I often have to take a step back and go through the routine again.

I recently took it to New Mexico where I was able to set targets at 200, 300, 500, 700 and 1030 yards and the rifle performed extremely well. Even in high winds later in the afternoon I was able to hold MOA groups at the 700 and 1030 yard targets.

 

[quiksilverj]

So I got it out to the range today and shot quite a few groups at 100yds prone. I shot suppressed, unsuppressed, wrapped thumb, thumb on the side, fingertip grip and 4 different kinds of ammo. Pretty much all the groups sucked. I had one lone group at .95 in and one all the way up to 2.4. The group average was 1.6 in pretty solidly no matter what happened. It is pretty consistently inconsistent. I also tried tuning the adjustable gas block which seems way over gassed suppressed and unsuppressed thinking this may cause some undo recoil but if I bring it down to where the bolt just locks back and then another half turn I have incredible reliability/stovepipe issues. I pretty much ended up right back where it was and still reliability is not great but that may be another problem.

I am pretty well at a loss with this rifle and where to go next. I would like to think it is me but I am starting to wonder. I worked in a decent number of dry fires today to double check everything and focused a ton on form. I really don't think I can pull the trigger of this gun any better than today. Also messed with the amount of slack today between the upper and lower which I don’t believe has any effect and after testing I still believe that the slop doesn’t matter.

 

[L.R.Novice]

I would say that slop matters. The slop between the upper and lower as well as the slop between the stock and the lower. Slop means that you can have variability from shot to shot. You don't know exactly where in the slop you are when you fire the round. You can torque the pistol grip to start reliably at one side of the slop but that is difficult to repeat consistently shot after shot. Torquing on a pistol grip that far from the bore results in a long moment arm that amplifies force and movement at the barrel.

I asked about the stock because I see a lot of people overlook that in ARs. I would eliminate as much slop as possible.

 

[quiksilverj]

LR Novice sorry I missed the post about the stock. I had checked that a few trips ago and it was solid. I think at this point I am going to tear the whole rifle down and retorque everything all the way back through just to double check again.

 

[quiksilverj]

As far as the slop between the upper and lower i tried to shim under the rear take down pin to remove any play there. It did work pretty well to take the play out but I couldn't muster any better groups. Not sure the best way to manage the play there if it is to drill and tap a set screw there? the fit seems ok between the 2 but i wouldn't say its stellar.

 

[Forward543]

Have another shooter shoot the gun and check it out. But then, get a new barrel. I went through 6 .308 barrels, with most getting in the +1 moa grouping. I found one 20" that worked. Just bite the cost and get a nice barrel. When i switched it to 6.5 cm the groups improved. It was a $600 barrel. If you cant make that one shoot, it is most likely that barrel.

 

[quiksilverj]

Update, I think I have the issue figured out. I appreciate all of your help and responses. I decided to tear the rifle down and go back and re-torque everything. Everything was tight after when I took it apart so I wasn't feeling very good about it fixing the issue. when I was tightening the barrel nut back on it stopped and I began to torque it and right before I was about to say good on the torque it moved another 1/8 of a turn and then felt solid. So with that I was pretty excited but not sure what happened. There are little set screws in there that set into the nut so maybe there was a small burr? Not sure and at this point I don't want to take it apart to check. I also believe I have the reliability sorted out which was too much gas but it was confusing because what seems to be the right amount of gas suppressed is about 3/8 of a turn open from closed which doesn't seem like very much at all. Anyhow I was able to get the rifle running well and get some groups down range and am happy to report it went very well. At this point it was just one outing but hopefully this will be the norm/ get better as I get more used to the rifle. Once again thanks for the help and suggestions!

group	inches	MOA
group 1	1.049	1.00
group 2	0.702	0.67
group 3	0.94	0.90
group 4	1.006	0.96
group 5	0.766	0.73
group 6	0.854	0.82
average	0.886	0.85