P.O.I. shift?

[KyleC]

What might cause a P.O.I. shift? Scope? Barrel seasoning?

Rifle: Seekins Havak Element
Scope: Leupold VX5HD 3-15x44
Ammo: Hornady Precision Hunter 143 eld-X
Range: 100 yards.


About 25 rds down the barrel. Groups were getting smaller the more I shot (3 shot groups).

 

[Frog4aday]

Wind? Bedding/stock issues? EDIT: Just tossing out some ideas you hadn't already mentioned. Interesting. Looking forward to seeing what other thoughts get put up here.

 

[Bart B]

You're shouldering and/or holding the rifle different for each 3-shot string.

Try shooting a 6- or 9-shot string.

 

[KyleC]

You're shouldering and/or holding the rifle different for each 3-shot string.

Try shooting a 6- or 9-shot string.

I think you might be right. Because I did change up my hold slightly and noticed the placement of the forend on my rest was different. I also might have noticed that since I am a left eye dominant, right hand shooter that my groups got better when I closed my dominant eye when shooting.

 

[David W Strait]

You're shouldering and/or holding the rifle different for each 3-shot string.

Try shooting a 6- or 9-shot string.

I think I understand why but at the risk of proving my ignorance, can you please explain why the POI change BartB?

 

[Bart B]

I think I understand why but at the risk of proving my ignorance, can you please explain why the POI change BartB?

Yes.

The rifle moves backwards while the bullet goes through the barrel. Recoil force is centered on the bore axis. As the center of mass holding the rifle is not on the bore/recoil axis, the bore axis angle and direction to the line of sight changes during barrel time.

Therefore, the bore axis at the muzzle doesn't point above the desired point of impact on target equal to bullet drop plus sight height until the bullet leaves the muzzle.

Anything that changes the recoil axis angle to center of mass holding it or the amount of resistance to recoil will change the bullet departure angle and direction relative to the line of sight when the round leaves the barrel. This is why the sight zero obtained from a bench top position will be up to 2 MOA different than those in field positions without artificial support.

 

[David W Strait]

Thanks for the explanation. I was on the right track but never had it explained in detail or read about it.

 

[19 Badger]

I have had similar examples of this as well. Which is why I will only go with drop data and groups(loads)that I have shot on more than one occasion in case I was having a good or bad day shooting. It happens... lol

 

[Canhunter35]

Parallax issues would be my guess.