Group size expectation for gas guns?

[frame12]

Looking for match results, or very large sample sizes.
Curious when you run your load out to 100 rounds or more and record and count every shot, what do you end up with for total group size?


I'll start. 2moa. 500 yards. counting ~250 rounds and 3 different projectiles and powders.

 

[Ledzep]

Rifle is now torn apart and rebuilt into a varmint rig, but last year I got 2nd overall in PRS gas gun. Generally speaking about 55-70% hits on PRS plates in KS, UT, SD matches.

20 shot groups were in the 1.7-2.1" range at 200yd (.85-1.1 MOA) when everything was tuned in. With it over-gassed, wrong muzzle device, etc. I had as big as 3.5" groups at 200yd (20 shots, also).

In general I think you can put together 1MOA gassers if you do everything right with quality components, but I also documented ~0.2 mils worth of elevation shift depending on fore-end loading with my beefy Seekins upper. Standard M4 uppers are much more, one of the other gas gun shooters at the finale was seeing more like 0.3-0.4 mils. I also saw bizarre dispersion (big fliers and complete lack of consistency) when you hard lock the handguard into barricades.

They are definitely finicky, but like I said, 0.75-1.0 MOA on a large scale is probably doable in a vacuum. In actual field use 1.5-2.5 MOA with the same system wouldn't surprise me.

 

[frame12]

...but I also documented ~0.2 mils worth of elevation shift depending on fore-end loading with my beefy Seekins upper. Standard M4 uppers are much more, one of the other gas gun shooters at the finale was seeing more like 0.3-0.4 mils. I also saw bizarre dispersion (big fliers and complete lack of consistency) when you hard lock the handguard into barricades.

huh.
Foreend Loading = leaning heavy into the butt stock while applying downward force onto the top of the hand guard or via a "gas pedal"?
When you say Hard Lock the handguard, are you attaching it with a clamp?

 

[frame12]

Rifle is now torn apart and rebuilt into a varmint rig, but last year I got 2nd overall in PRS gas gun. Generally speaking about 55-70% hits on PRS plates in KS, UT, SD matches.

20 shot groups were in the 1.7-2.1" range at 200yd (.85-1.1 MOA) when everything was tuned in. With it over-gassed, wrong muzzle device, etc. I had as big as 3.5" groups at 200yd (20 shots, also).

In general I think you can put together 1MOA gassers if you do everything right with quality components, but I also documented ~0.2 mils worth of elevation shift depending on fore-end loading with my beefy Seekins upper. Standard M4 uppers are much more, one of the other gas gun shooters at the finale was seeing more like 0.3-0.4 mils. I also saw bizarre dispersion (big fliers and complete lack of consistency) when you hard lock the handguard into barricades.

They are definitely finicky, but like I said, 0.75-1.0 MOA on a large scale is probably doable in a vacuum. In actual field use 1.5-2.5 MOA with the same system wouldn't surprise me.

also, what bullet / powder are you running?

 

[Ledzep]

huh.
Foreend Loading = leaning heavy into the butt stock while applying downward force onto the top of the hand guard or via a "gas pedal"?
When you say Hard Lock the handguard, are you attaching it with a clamp?

Bipod and rear bag vs. fore-end rested on a heavy sand gamechanger.

Locked in like pressed hard directly against the barricade, most notably at the bottom "crotch" of a tank trap.

also, what bullet / powder are you running?

6mm ARC with 108 ELD-M, 109 ELD-M, 110 A-tip. LeverEvolution and Varget for powders, was able to achieve good results with various combinations of bullet/powder/muzzle device. Gas gun dispersion seems to be more linked to muzzle device than what I've seen in bolt guns.

 

[frame12]

Bipod and rear bag vs. fore-end rested on a heavy sand gamechanger.

Locked in like pressed hard directly against the barricade, most notably at the bottom "crotch" of a tank trap.


6mm ARC with 108 ELD-M, 109 ELD-M, 110 A-tip. LeverEvolution and Varget for powders, was able to achieve good results with various combinations of bullet/powder/muzzle device. Gas gun dispersion seems to be more linked to muzzle device than what I've seen in bolt guns.

That kinda opens up a whole bunch of factors... Inconsistent loading could read as velocity spread for one.
Interesting.
I added a bunch of weight on my hand guard. Didn't weigh it, but maybe 3 or 4lbs. It balances well with it, though.
No muzzle breaks allowed in F-Class or BR, so I just run a thread protector.
getting off topic.
Thx for the info!

 

[Ledzep]

It will show up at whatever distance you care to check it. Off a bipod will be on zero, off a bag/barricade will be 0.2 mils low. Run a chronograph at the same time if you want to rule out velocity.

Even if you place the bipod on uneven levels (left leg dramatically higher than right) and induce a torque, you will start to see horizontal shifts. It's what you get for using an aluminum receiver and putting the load bearing lever arm on the same piece that holds the barrel to the optic.