Had a HS problem w/ a barrel swap recently. Used a go-gauge & found fired cases matched the go-gauge H/S. But, W/ die set to S/H + 1/4 turn, F/L sized cases were .0015" longer & difficult to chamber. Chkd my shell holder & found it measured .246".... I could shorten the S/H or cut about .003" off bottom of die to get the amount of sizing flexibilty I needed. I decided to order three more S/H's from different Mfg's. here's what I got: S/H (A) .223", (B) .250" (C) .261" That's .038" difference in S/H's. ( industry standard is .250") If I didn't have a comparator & simply set my F/L die to the (A) S/H would the case have gone KABOOM from the massively short H/S? Maybe---maybe not. Without a doubt results could be head separation after a few firings or cratered primers or both, even if powder chgs had been worked up slowly. I really don't think setting HD SP w/ a F/L sized case is the best idea. If the above happened to me, it could happen to anyone. Rare circumstance? YEP! Could this happen to a novice BBL swapper w/ no go-gauge or comparator?.......................................