Bench VS. Prone

[trammerbammer]

I'm not sure if this is where this topic is supposed to be, but if its in the wrong place oh well. I've zeroed my scope while using a bipod while laying prone. I took my rifle to a range for the first time ever, and I'm getting groupings 4 inches high, and 2 left. I have been told that is because I've set up on the grass, and the recoil is taken different on a bench. My question is this: If I zero my scope at the range, will it be zeroed on grass. Any input would be great, thanks.

[Jim White]

- (Hate to ask) but are you sure it was sighted in with the same load you tested in the grass?

- Is there a clear path between the muzzle and the target (are you shooting thru the grass?)?

- In both instances, was anything touching the barrel?

- In both instances, was anything touching the scope?

- In both instances, was the eye relief, cheek/stock-weld the same?

- Is there parallax in the scope?

- When you sighted in the rifle did you re-verify zero after the windage & elevation caps/covers were reinstalled (if equipped)?

- Inspect the rig and check for any changes/movement?

- Did something happen to the rifle (ie...dinged crown)?

- Is the rifle bedded? If not, was there a significant difference in the weather conditions between sight in and testing in the grass?

If your rifle is bedded, free-floated, has a decent barrel, has a good load and a properly mounted scope that was correctly sighted in the rifle should hold zero whether in the grass or on the bench (I'm presuming you're not shooting through the grass and there is a unobstructed path between the muzzle and the target).

HTH,

[trammerbammer]

Same load, clear path, nothing touching barrel or scope, eye relief was the same, parralax was set to the distance I was shooting, I did not re-zero after turret caps were put back on, but it was still shooting dead on, I baby this rifle so the scope shouldn't be knocked. And no, the grass is too short where I'm shooting for it to be in the way. Thanks for the help.

[Jim White]

Have you tried shooting it again and if so, did the "zero" hold or did it shift again? You didn't mention what type of rifle it was but the head/eye position behind the scope does come into play. To rule out the scope try the box test and see if it tracks.

[Glen]

The bi pod legs won't move the same on grass as they will on a bench. On a bench they slide more freely. In the grass they will hang up on the grass or maybe even a small rock & jump. HTH

[OldTurtle]

The bi pod legs won't move the same on grass as they will on a bench

+1...
I've found that even shooting off a bench, there is a distinct difference between using a bare concrete bench and placing a piece of carpet sample under the bipod...Your point of impact will change..

[Critter]

This question is not as simple as it seems at first blush. This is a question of the torsional deformation of an indeterminate structure under dynamic loading.

1. However, there is no doubt in my civilian mind that the point of impact will change.

2. Having said that, then the next question is how much!

If you have a bedded action and a free floated barrel, then the stability of the fore end comes into play. My feeling is that if you have a heavy duty tactical stock then the deflection in that member will be significantly less when compared to light varmint stock or wood hunting stock.

My experience with tactical rifles of heavy construction is that the effect is minimized at normal (<800 yards) ranges.

Of course, your experience may vary.

[Jim White]

I went back and looked over some of my old scoring books from my highpower service rifle (M14) days and here is what I determined;

With a McMillian heavy stock, heavy & free floated barrel, and double lugged action my zero's never changed because of sling tension from the standing (no sling use) sitting rapid and prone rapid/slow fire. They would change if the head position/stock weld wasnt right.

With a heavy stock, light & free floated barrel and no lugging, the zero would shift, especially in the prone position.

I don't have a lot of experience with bi-pods but I now have a 300 WBY that supposdly wouldn't shoot. I took off the bipods went to the range and it shot dime size groups @ 100 yds. I took a picture and sent it to him and borrowed an ole' USMC Gunnery Sgt quote;"...there ain't nothin' the matter with that rifle, keep it tight..." Maybe something is different between the two set-ups.

To quote Critter; "...you're experience may vary..."

HTH,