Grouping change in different positions


May 10, 2003, 08:24 PM
I have a problem of my groupings changing when I switch postions during highpower competition.

My club fires the standard NRA, standing slow fire, sitting or kneeling rapid fire, rapid prone and slow fire prone. We shoot using the 100 yard substitute targets

I'll get the rifle to a good group in standing but when I go to the other positions and use the sling my groups drop drastically low and right. I have trouble figuring out the sight adjustments for this.

Could the problem be from moving my eye closer toward the rear sight due to positon and the sling?

Could it be the sling causing this?

I'm not sure if what is causing this or how to correct it.

Maybe this is natural (I only started highpower shooting last year) and if so, what is a good way to go about finding out how to do sight correction.

BTW, I use am M1A in this competetion, but I have noticed the same thing with an M1.

Thanks in advance for your help.

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Art Eatman
May 10, 2003, 08:31 PM
Any change in sling tension, whether from shot to shot or in different positions, will affect the pressure of the stock on the barrel or receiver or both. Thiis change in tension need not be large to change the location of the group center.

Either standardize your use of the sling and maintain constant tension, or learn the amount of movement and either dial it in to your sights or use "Kentucky windage". The former method is most likely better. :)


May 10, 2003, 09:51 PM
Your sight settings should change with each position. It is not possible to get on the stock in the same way from the various positions. If you're using a scorebook, which really is necessary, record the different sight settings for each position and use that as a beginning point when you shoot your sighters. Then refine from there depending on where your sighters go.

Andrew Wyatt
May 10, 2003, 10:18 PM
i've seen this happen before, and it's sometimes drastic.

my dad's friend has a sako in .375 that was worked on by robar.

standing, the rifle is zeroed when the rear sight is centered in the notch.

prone, the sight needs to be moved a full quarter inch left, because the stock comb has a pronounced wedge shape to it, and in prone, the head slides to the left in relation to the stock centerline.

May 10, 2003, 10:35 PM
Thanks for the help.

I'll go out to the range this coming week and shoot individual rounds in each position and record the sighting changes in my book.

May 11, 2003, 12:10 AM
The reason your shots are lower when sling is used is it restricts the recoil of the rifle. Your sight setting compensates for the fact that the bullet is still in the barrel during the beginning stages of recoil, therefore, in offhand, most competitors do not grip the forearm but let the rifle just rest on the left hand (for right handed shooters) the recoil is greater resulting in a higher hit.

As M90A1 said, you will find that each position requires a different sight setting. My prone slow fire sight setting is different from my prone rapid fire setting because I use a slightly tighter sling on rapid fire than slow fire (can get by with tighter sling for 70 seconds than I can stand for 22 minutes). Also good advice to get a score book and record your sight settings at each shooting session (practice or match). You will soon find the precise "zero" for your rifle at each stage.


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