Bullet stability varies with twist, bullet length, bullet density, air density, bullet shape-maybe, and bullet velocity-somewhat.
Cast bullets that are tipping = making elongated holes in the paper, are sometimes very accurate.
I have been unable to make .30 bullets tip as powder charge/velocity decreases, they just shoot bigger groups as velocity decreases.
Some bullets at some velocities go through the paper sideways-not tipped-sideways. These are always wildly inaccurate, so far.
Some bullets at some velocities are wildly inaccurate, but show no sign of tipping.
1/20/17 Savage Striker 22-250, 14” twist, 225646M, .692” long, Greenhill minimum twist required = 11” per turn, 8 SR4756. This shot 1 off the paper, 5 into ~6”, and 3 with another aiming point into ~7”. This load and gun have been reasonably accurate in the past. If there is any tipping, it is slight.
Without cleaning, same Striker, same shooter, same day, same range; Midway Dogtown 55 gr SP, 8.0 SR4756, .8, 1.0, .85, 1.175, .7; AVERAGE .905.
It was in the 50s at the range, much of my shooting is in the 80s and 90s.
This 14” twist shouldn’t stabilize the 225646M at .692”, or the Dogtown bullet at .700”; but it does, at least most of the time.
Could the increased air density cause a marginally stable bullet to become unstable and shoot wildly, at low temperature?