Different shooting positions, different POI

T

tangolima

New member
I know the POI will likely shift if I hold my rifle differently. It is just some interesting observation, and would like to confirm with other shooters.

I zero a rifle on bench rest, not sled, with front and rear rests. When I fire the gun, my right hand is on the trigger while my left hand is squeezing the rear rest to adjust the aim.

When I am done with zeroing, I shoot the gun in field position, say prone. My left hand supports, not grabs, the front of the rifle similar to the front rest. POI will be consistently 3-4 MOA lower.

3-4 MOA sounds a lot. But translated into muzzle drop, it is like 0.02", or half a mm. I can see it is quite probably to be caused by change in position.

Do you observe the same? Thanks.

-TL
 
Yep. If you like shooting from a bench, zero on a bench. If you prefer field positions, learn your zeroes for each position you are likely to shoot. A sling supported position will also change POI from an unsupported position.

I have a friend who zeroes his rifle with a lead sled. I prefer to get a zero from bipod/prone or whatever position I am likely to use.
 
I've never seen any difference. Sighting in at the bench, the front sand bag is where my support hand would be when in the field.

The result has been that when I aim at the white spot, I hit the white spot and Bambi hits the ground.
 
It's normal to have a lower POI when shooting from a position that supports the rifle more solidly(prone vs benchtop). I've seen heavy barrelled 300 Win mag target rifles change POI significantly when fired from different positions due to the difference in recoil attenuation.
When you fire from the supported bench with your left hand under the toe of the stock, the unfettered front of the rifle rises and tries to rotate around the resistance point-your shoulder which moves back under recoil. When fired prone, even the small amount of control imparted by your left hand combined with more resistance to recoil causes less rotation around the recoil point(your shoulder) resulting in less vertical movement while the bullet is in the barrel.
 
I don't know about shooting from the bench, but I do have a different sight setting shooting 200 yard standing vs. 200 yard rapid fire.

I honestly believe it because in rapid fire I have a tendency to bleed into the black a bit.

Also my head position (eye relief) is different.
 
I used to shoot off the bench with a front mount BR bipod with a rear bag, and found I get better groups with a Rock BR front rest and rear bag.
 
Every shooting position will have it's own zero. Some will be so close as to be insignificant. Others will require sight adjustments . The only real way is to shoot the position and record the results. Of course then there are weather conditions that can affect the POI.
 
Absolutely.
Frank Galli from the Hide has a video on this on YT- prone to bench affects his POI by a full inch, IIRC,
 
I understand the zero will change when I change shooting position. But it is the way it changes that interests me. Seems the poi always drops when I get off the bench rest, as much as 3 MOA. It was alarming at first. But when I convert it into muzzle drop in thousandth of inch, I can see how easily it can come about. I already try to emulate the bench rest by supporting the forend, instead of grabbing it.

-TL
 
You may be using something fairly hard for a rest such as actual sand in a sand bag when shooting from a bench. That will often cause you to shoot higher. I fill by sand bags with cheap cat litter which makes a softer bag. Then shooting prone with my palm for a rest I get the same zero.
 
math teacher said:
You may be using something fairly hard for a rest such as actual sand in a sand bag when shooting from a bench. That will often cause you to shoot higher. I fill by sand bags with cheap cat litter which makes a softer bag. Then shooting prone with my palm for a rest I get the same zero.
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I do have real sand in my rest. But I don't know how much difference it will make as the rotates up during recoil. I will give it a try. Thanks.

But wait, are you talking about the rear bag. I can see the firmness of that bag could probably make a difference.

-TL
 
Both bags. Real sand compresses to where it is effectively almost as hard as a rock. A gunsmith put me onto using cheap clay cat litter. He suggested cutting off a piece of old pant leg, sewing one end, filling it with cat litter, then sewing the other end. That is what I use and it works great. Been using the same bags for years. I carry a bag in the Jeep while moose hunting for an impromptu rest. Don't use clumping litter. Crystal litter works great in your gun safe to absorb moisture, but is too fine for bags.
 
3-4 MOA sounds a lot. But translated into muzzle drop, it is like 0.02", or half a mm. I can see it is quite probably to be caused by change in position.
Click to expand...

I realize shooting off of a hard surface can make the gun shoot higher, the part that's confusing to me is the above statement.

3 to 4 MOA is a lot with all my scoped rifles and computes to a lot more then 2 tenths of an inch in change of POI.

Maybe I'm misreading something.
 
POI shifts 3" at range of 100 yards, so 3 MOA.

100 yards is 3600". My rifle has sight radius of 24" (I am using iron sights, but same applies to scope).

The equivalent muzzle drop for the poi shift is given by

3 / 3600 * 24 = 0.02" or 0.5mm

Not much indeed.

-TL
 
You must remember that recoil begins when the bullet begins moving forward. At that time, the stock begins it's (much smaller) move to the rear. The variations you note are due to the rifle's movement being different between being held in a rest, or a bag or solely by a human. My match (AR) rifle does print about 2" lower from prone than it does from bags. You are not alone.
 
When zeroing hunting rifles, I usually place my left hand under the forend and resting on the front rest bag.

My rifles have free-floated barrels, which minimizes barrel jump when shooting from different rests/positions, but causes variations in POI when shooting different bullet weights/powder charges.
 
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