It's velocity, not pellet deformation.
A longer barrel typically equates to higher velocities.
I got the worst spreads from the rifles I tested shot shells in.
Using the same .38 load, for instance, at the same distances, and shooting it from a snub Smith to a four-inch Smith revolver to a Marlin 20-inch levergun, it was possible to see the rate of pattern spread grow with each barrel length and increase in velocity.
This was consistent across other calibers and barrel lengths.
Rifling twist has SOME effect; if one revolver has a faster twist than a comparable revolver in another brand, the revolver with the slower twist will shoot a tighter pattern at the same distance.
Denis
A longer barrel typically equates to higher velocities.
I got the worst spreads from the rifles I tested shot shells in.
Using the same .38 load, for instance, at the same distances, and shooting it from a snub Smith to a four-inch Smith revolver to a Marlin 20-inch levergun, it was possible to see the rate of pattern spread grow with each barrel length and increase in velocity.
This was consistent across other calibers and barrel lengths.
Rifling twist has SOME effect; if one revolver has a faster twist than a comparable revolver in another brand, the revolver with the slower twist will shoot a tighter pattern at the same distance.
Denis