Benchresting for accuracy: bolt gun vs. gas gun?

My Toy said:

When benchresting a rifle to determine accuracy of any given load is there any difference in the technique used for a gas gun (AR-15, AR-10) as opposed to a bolt gun?
For years I've been using a front rest /w bag and a rear bag for my bolt guns and been getting great consistent results. I know my gas guns mentioned above are not as accurate as my bolt guns and won't achieve the same level of accuracy but what I'm really talking about is consistency of results.
When benchresting my AR's with a given load in the same session some of my groups will produce reasonable accuracy for the rifle and the next group with the same load/gun will open up.
I think my gas gun are capable of better more consistent accuracy than I'm getting and I'm wondering if it might not have something to do with benchrest technique.

Click to expand...

E.Shell said:

What size/shape/distance are your AR groups. How do your bolt gun groups look?

A correctly 'smithed precision AR-10 or AR-15 with good optics and good ammo will shoot to less than 1/2 moa, sometimes, much less. Is this what you have?

If not, and you have an average production rifle, you'll not equal a precision rifle (bolt or semi) no matter what you do wrong or right.

If you do have a precision AR and it is mechanically sound, it should have potential, but there can be any number of issues preventing best performance.

Ammo: What kind of ammo are you using? Good quality match grade ammo? If not, look no further.

If your ammo is not the limiting factor, how about sights/optics? Are you using a higher magnification scope with a precision/fine reticle? You cannot shoot any better than you can see.

If you're not working against hardware issues, the single biggest thing is to control recoil without putting the rifle into a death grip. Bolt guns are kind of 'dead' on the bags compared to the dynamics of an AR. Further, most bolt guns are more rigid than ARs and will be more forgiving of torquing/bending the rifle to push it into the target. Make sure it is sitting solidly on the bags and is not being torqued. Use the firing hand to pull the rifle back into your shoulder without using the thumb.

If this doesn't help, you may benefit by having a gunsmith give the rifle a once over, and/or get a shooter experienced with ARs to try your rifle and see if they can isolate the issue.

Click to expand...

My Toy said:

...The Armalite will shoot a 5 shot groups with 3 shots in a cluster ( probably 1 MOA) and 2 shots that open the group up to 3". It is not necessarily the last two shots that open up the group; but typically there will be a couple tightly clustered and one, two or three away out.
This is why I started to think it may be benchrest technique that is OK with my bolt gun but less than satisfactory with configuration of a gas gun.

Click to expand...

E.Shell said:

Aside from the difference in magnification, I would suggest that handling is very likely the issue, as you suspect. One thing about AR-15s, and AR-10s in particular, is that they are quite flexible, like a spring, and they will store any energy that the shooter imparts in the form of pressure. The AR-10s are more reactive due to a greater recoil impulse.

Bolt guns are far less reactive on the bench, and thus less susceptible to rough handling. The biggest benefit one buys with a custom stock for a bolt gun is rigidity. Rigidity = stability = forgiveness....in the sense that a 'hard' stock doesn't store energy like a flimsy one will. A good example of this is the gradient between the cheap 'TupperWare' style injection molded plastic stocks. They are very flexible and extremely difficult to shoot well. Next step up is the Hogue, then the HS Precision stocks, both of which are less flexible and springy than injection molded units. Next stop up is a custom stock like the McCree, Manners or McMillan, which very 'hard' and essentially lay dead on the bags. One can get away with a LOT more mishandling when using a solid stock like a McMillan.

For example: If you push your right cheek against the stock to make the crosshair move left, the rifle will work against this during recoil and bounce away from the pressure point, making the bullet leave the group toward the left - same direction the rifle is being pushed. Same if you lift the gun off the rear support to bring the crosshair down - the rifle with push away from the pressure point and likely hit low. You can 'hold' the rifle on target and think it is rock solid, but it can be like a compressed spring that releases during recoil. More flexibility = more stored energy = more reaction to mishandling.

Your cheek should lie straight down on the comb and not move the gun sideways as you take a cheek weld. If it does move sideways, your natural point of aim needs work and you may be too straight behind the gun.

Your firing hand should pull straight back toward your shoulder, which should be in firm contact with the butt. Twisting the grip, pushing with fingertips or thumb will cause bullets to leave the group. The rifle should be solidly trapped between your cheek and rear support, between the firing hand and the shoulder, with no lateral or vertical strain. When you're all set to fire, you can let go of the gun to see how badly you are wrestling with it. The only motion should be a slight downward drift of the crosshair as you lift your head off the stock.

Take care when shooting at a bench that your stool position doesn't force you into an artificially upright position. if so, you will not control recoil properly and will see vertical stringing. Lots of shooters start off OK, but the gun works them backward during recoil and they just sit up straighter and straighter, instead of pushing the rifle back forward.

Click to expand...