A fast twist barrel will cause the SX bullets to come apart. I have had vapor trails and disintegrated bullets with them in a 1 in 9 barrel. Supposed to keep velocity under 3500 fps, but I ran them at full velocity in a Ruger #1 in .22-250 with no issues and my cousin ran them full throttle in a .220 Swift. Both barrels were 1 in 14.
