A barrel of less that 7.5" will NOT spin the bullet properly to stabilize it in flight
This I didn't know - the classes in ballistics I've taken say otherwise... such as, handguns still stabilizing bullets, short barreled rifles still stabilizing bullets, etc. I'll have to read the threads over on ST, I'm PTK there same as here.
EDIT: I read those threads (and participated in one a while back) and neither says anything about the twist rate vs the length vs the velocity effecting bullet stabilization. I don't see how a shorter barrel won't stabilize a bullet (other than VLD bullets, that's easy to understand) for things like 55gr... I mean, my PLR-16 will stabilize 69gr bullets quite happily, no baffle strikes. But then again, it's a 9" barrel.