A lot of the posts in this thread crimps my style. Such is life.
Nobody shooting centerfire rifles winning matches and setting records ever crimps a bullet. Tests with rail guns fired in free recoil with the best of everything used to load shoot the very best match bullets into the tiniest groups possible......ever crimps a case mouth. It adds another (huge) variable to the ammo by causing large spreads in case neck tension on bullets.
Decades ago, military arsenals used to crimp .30-06 match ammo bullets in cases just like regular service rounds are made. 'Twas either Hatcher or Whelen that said they really shouldn't do that 'cause it hurts accuracy. So one arsenal ran a lot of match ammo with half the cases crimped with different amounts of case mouth curl and the other half had no crimp at all. Since then, all arsenal rifle match ammo's never been crimped. And the scores were better too.
Uncrimped ammo shot the most accurate. As ammo with crimp was tested, the more the crimp the more the test groups open up.
So......if anyone feels a need to crimp their centerfire rifle bullets (save those used in 35 caliber and larger monster mashers) for best accuracy.....think again. Your're doing something pretty attrocious with your hand/re-loading tools and/or processes that's masked by crimping in your bullets. Or, you just happened to shoot the tiniest few-shot groups with crimped ammo and thing its the best thing since dollar bills. Some will never understand. Others may do so and end up with uncrimped case mouths on ther bullets shooting them more accurate.