Point of Aim and zero shifts

[no_problem]

So, I am at the range shooting 100 yards. I started to wonder about zero shifts.

Assuming that you are zeroed in with your favorite rifle and high quality scope solidly mounted on your gun and properly zeroed. Does your Point of Impact (POI) vary from your Point Of Aim (POA) if you change from, say the bench to the hood of a cruiser, or if you move from your trusty bipod to some sandbags, or a backpack?

In other words, does POI change if you change your rest or your body position? And by how much would your POI shift?

 

[adobewalls]

The answers are:

"Yes"

and,

"It depends"

You have to shoot your load and your rifle and know what it will do.

Settling a rifle down into a pile of sand bags, and touching off rounds may not be any where near where the POI is when you are in the woods and take an off-hand shot. BUT the only way you will know is by actually shooting the rifle from the positions and situations similar to what you think you will have when you get that "money" shot.

I reload, and in my early years I developed some top end loads that were also accurate - but making nice little groups off of sandbags, and being able to repeat that off-hand was not going to happen until I backed my load down.

 

[Navy joe]

My most educational rifle thus far is a Ty 38 Arisaka that bubba worked on. I've got it doing a consistent 1.5 a 100yds, but my the work! 30" pencil barrel that is not floated. Move your hand a few inches, POI shift. Rest the forend on a solid rest, better get another target because POI is moving. A foot. So, as above, "Yes" and "It Depends"

 

[30Cal]

The more the rifle recoils (or conversely, if the bullet spends a long time in the barrel as in the case of an air-rifle or long barrelled target rimfire), the more you'll see changes in POI due to position.

If you shoot with a sling supported position, you may also see a change in impact due to sling tension.

 

[W.E.G.]

If you zero from a benchrest, you will definitely see a change in point of impact if you kneel and rest against the side of a post. This is why you must practice all your field positions, and zero for the position you are most likely to use in the field.

 

[Art Eatman]

All of the above responsses go to show how changing the point of pressure on the barrel affects POI. The common solution is to free-float the barrel in the forearm.

I free-float my barrels and then use a little shim as a vibration damper. I'm thus careful to place the rifle for sighting in at the same place on the forearm as where my hand is when in the field. So, I don't have the POI shifts...