T3PRanchThe faster a projectile passes through a rifled barrel the higher the rotational velocity and generally the greater the stability.
Thurmond
Tom Gaylord did a fairly lengthy test on the effect of various twist rates on pellet accuracy. Look it up on his PA blog."bill_dd97"
"T3PRanch"The faster a projectile passes through a rifled barrel the higher the rotational velocity and generally the greater the stability.
Thurmond
To a point. I know in powder burners using jacketed bullets, a fast twist rate on a light round will destabilize and tear it apart. You also must remember that pellets are primarily drag stabilized and rotation only assists stability. As far as I know there are no studies that determine optimal twist for pellets. I do know that Harry has done screen testing for smooth twist and traditionally rifled barrels. I don't think Harry's data supported any conclusion of which was better.
I have not found the actual twist that is applied to the Smooth twist barrels though.
Interesting point about that... a bullet can be torn apart by centrifugal force alone, even if it's perfectly stable. A typical .223 Remington bullet leaves the muzzle at somewhere around 3,000 FPS. From a 1:8 barrel, it's rotating 4,500 times per second, or 270,000 RPM. The centrifugal force on the jacket is over 200,000g."bill_dd97"
I know in powder burners using jacketed bullets, a fast twist rate on a light round will destabilize and tear it apart.
bill_dd97
Different pellets, whether design, weights or caliber will perform differently in the same barrel.
Or your 25 and 22 barrels aren't indexing exactly the same so there is a horizontal shift between them.
KitplanenutNeed to be packing a journal.
No 2 barrels are the same. I would bet my money that no 2 Impact barrels, even if they are in the same calibre will have the exact same poi at 50 yards."Kitplanenut"Let me explain what I was trying to figure out. On my Impact when I changed barrels from sighted in 25 to the 22 there was about a 1 MOA drop at 50 yards. I can understand that. But there was also about a 1 MOA move to the left. That I couldn't understand. Then I remember reading that twist rate could move POI horizontally. Was wondering if that was causing it. Also there was a difference in the horizontal movement between the 15 and 18 grain pellet. That got me to wondering about the 25 cal, so put that barrel back on. POI was the same as when I took it off, but there was a difference in horizontal movement between the 25 and 33 grain. Now, this horizontal movement is just mice nuts, but enough to notice and got me wondering why. I'm sure someone has a logical explanation. And before someone starts putting it down, I'm completly satisfied with the Impact.