POI shift horizontally with different pellets???

[toku58]

I was shooting my .22 the other day and wanted to see how my gun would shoot different types of pellets.

So JSB 18.13 gr hits pellet on pellet at 25 yrds.
When I switch to PolyMags it consistantly shoots 1 mil. to the right at 25 yards? (Not much difference in elevation.)

I'm trying to wrap my head around what is going on? I can understand a height shift from different pellets. (Different gr)

But? How does it shift horizontally?

I go back to the JSB and they are spot on.

Anyone have an idea of why it would do this?

 

[stinkajames]

I have always assumed that this is due to slightly different harmonics in the barrel with different pellets. As in the pellet would exit the barrel at a slightly different point in the barrel "whip", which could be in any direction, causing the downrange POI to be out. Reading your post makes me wonder whether a heavy bull barrel would not change as much with different pellets? What gun are you shooting and is it a thin barrel? 
James 

 

[Stone02]

IME different pellets can change POI any place, through 360°.

 

[Guest]

A shift in poi is not only common when using different pellets but expected. The differences in shape alone are the major cause. You wouldn't expect different pb rounds(shape/weight) to impact in the same place either. 

 

[Keyman62421]

The difference in recoil, i hear many say , air guns have no recoil. Equal and opposite reaction (recoil). Ever so slight / ever so there!

 

[toku58]

"stinkajames"I have always assumed that this is due to slightly different harmonics in the barrel with different pellets. As in the pellet would exit the barrel at a slightly different point in the barrel "whip", which could be in any direction, causing the downrange POI to be out. Reading your post makes me wonder whether a heavy bull barrel would not change as much with different pellets? What gun are you shooting and is it a thin barrel? 
James 
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Thanks James!
This makes sense! I'm shooting my Impact "X"
So now it makes me wonder if the POI will continue to change the further out I go?
But since it's the "X" model.
I'll try and make note of the liners position and see if rotating the liner 90 degrees will correct this issue?
I'd prefer to have the POI shift vertically rather than horizontally.

 

[-edge-]

just using mk2 and mk1 34 grain .25 gave me about 5 moa difference horizontal

 

[stinkajames]

"toku58"

"stinkajames"I have always assumed that this is due to slightly different harmonics in the barrel with different pellets. As in the pellet would exit the barrel at a slightly different point in the barrel "whip", which could be in any direction, causing the downrange POI to be out. Reading your post makes me wonder whether a heavy bull barrel would not change as much with different pellets? What gun are you shooting and is it a thin barrel? 
James 
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.
.
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Thanks James!
This makes sense! I'm shooting my Impact "X"
So now it makes me wonder if the POI will continue to change the further out I go?
But since it's the "X" model.
I'll try and make note of the liners position and see if rotating the liner 90 degrees will correct this issue?
I'd prefer to have the POI shift vertically rather than horizontally.

sounds like an interesting test mate. I have an Impact x 22 arriving soon so would love to hear how you go with it.