POI Question

[Duckslayer12]

Had a talk with one of my friends father today. He said if you have a, lets say 60gr bullet zeroed at 200 yds in a rifle chambered in 6mm using only Hornady factory ammo. If my friend uses the 60gr bullet for varmints and switches to a 100gr bullet for deer, the point of impact will only change up and down and not left and right? I have a hard time believing this since I shoot .22-250's for varmints and see different impact changes with different weights of bullets all the time.

 

[xNF_9]

Re: POI Question

One thing I can see is that if the rifle twist on the barrel is too slow for shooting a 100 gr bullet. If it can't stabelize the bullet it can change left to right.

 

[desertHK]

Re: POI Question

I can also change left/right as well. It depends on the condition under which you originally zeroed the 60 grains bullet. If you have lots of wind during the zero process, then a heavier bullet will be able to buckle the wind and deflects less than the 60 grains. Of course, at 100 yards, you may not see a whole lot of that left/right changes, but as the distance of zero increases, that can change.

 

[proneshooter]

Re: POI Question

Assuming the current zero on the rifle is a no-wind zero, your friend is correct.

However, even when there is no wind, there will be a sideways zero shift when shooting at really long distances due to the Coriolis effect.

I can tell you for a fact that my zero changes laterally between 600 and 1000 yards.

 

[gams100459]

Re: POI Question

Duckslayer,
I agree with you. Almost every rifle I reload for prints a different poi for any given powder charge, or bullet combo. While load testing, I just shoot for the group, and don't care where the poi is. After deciding what shoots the tightest group, I adjust my scope.
I try and keep notes as to where my scope settings are for each bullet and powder combo. This makes it easier when switching from one to another. I'm working on acquiring different rifles for each application.
Hope this helps
Gam

 

[BK7saum]

Re: POI Question

I've had heavier bullets shoot to a higher point of impact and lighter bullets shoot to a higher point of impact. I've also had the point of impact shift left or right when switching between loads.

Do the barrel harmonics cause the barrel to move only in a vertical plane? I really don't think so.

The short answer is that when changing loads or ammunition, your POI can shift in any direction based on what I have seen from several different rifles.