I don't use "gun vices", I check my loads the way I'm gonna shoot them. Normally I use the high power positions to develop my loads. Setting, Prone, etc. using the sling un-supported.
Same with my hunting rifles. But I don't shoot 3-5 round groups, I shoot 10-20 round groups.
It gives me a better ideal what is gonna happen in a match or in the field.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071