Barrel fit is as much or more of a factor than velocity, but soft lead bullets tend to lead more when they get close to 1000 fps.

I think taper crimping revolver rounds is fine if that gets you the best results. But if you have a lighter gun and heavier loads, the bullets may tend to back out by the time the last round is fired. A very slight roll crimp can usually prevent this.

I have a very light alloy J frame 38 special that would probably be worse on backing bullets out than most guns. Shooting the same load in my 686 probably wouldn't budge them one iota.

My old Speer #9 did a test with increasing loads with various levels of crimp. Only the non-crimped bullets at heavy loads showed signs of bullet backing out.

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