Re: Neck Crimping
I crimp the hand loads for some of my rifles and find that it does help. The caveat is that most of the rifles I shoot are sporterized milsurps that have the original military barrels. They usually have "generous" chambers and leades that are long enough that I can't seat the bullets anywhere near the lands.
For example, I have an M44 Spanish Mauser (8x57) that my dad gave me that would shoot 3" 5-shot groups uncrimped, but that dropped to 1" crimped. I get the same type of results with 2 7x57 surplus rifles, one Mexican 1910, the other Dominican republic. The DomRep one has a slightly under-length chamber (almost closes on the Go gage) but still has on oversized throat. To get new brass to chamber easily, I have to resize it with a 0.005" feeler gauge between the case head and the shell holder.
Lever action (or anything else with a tubular mag): Get a bullet with a cannelure and roll or factory crimp in the cannelure.
Semi-Auto: Probably should be crimped, but I know quite a few people who don't and it works fine.
For a bolt-action rifle with a normal chamber and leade length, crimping shouldn't be necessary with proper neck tension and a reasonable jump to the rifling. I have a 257 roberts that I had built on a Yugoslav mauser receiver that does 1" groups at 200 yards with 115 gr Nosler BT uncrimped and 0.020" off the rifling, but that group size more than doubles with the crimp. That's what I expected, but I wanted to experiment with it anyway.
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