Crimping questions

[Daveintheburbs]

I would appreciate discussion on the desirability and techniques for crimping magnum rifle/revolver rounds used for hunting. Currently I work up all my heavy loads with a substantial Lee factory crimp as a last step. I know it is not accuracy enhancing, but I want to ensure the bullet stays put through heavy recoil. What are other folks doing and how?
Thanks,
Dave

[Paul H]

Actually I would not say that the lee factory crimp doesn't enhance accuracy, as often times it does just that.

Typically for heavy handgun loads, I use a moderatlely heavy crimp. I had been using a gorilla crimp, but case mouths started to split after a few firings and I leaned back a touch.

For rifles I typically don't crimp until getting up my monster mashing 458 Lott, and I'm not sure that is so necessary. The top end loads are heavily compressed, so the bullet really has no place to go.

With heavy handguns, the recoil acts like a bullet puller so a heavy crimp keeps the bullet in place. Also the slower burning deterant coated ball powders really seem to like some resistance before they start burning well, so the heavy crimp does seem to benefit accuracy and consistant velocities.

[Daveintheburbs]

Hmmm

Paul, have I got the basic Physics wrong? I was worried about my loads increasing OAL. My top ends are pretty packed as well esp .375 H&H.
Dave

[Paul H]

In a handgun, the bullets will increase in OAL, as there is nothing to stop the bullet as the case moves rearword in the cylinder. So the crimp keeps the bullet from being pulled out.

In a magazine rifle, what happens is as the rifle moves backwards, the cartridge wants to stay where it is until the front of the magazine hits the bullet. Look at your magazine and you should see some indentations where the bullets have been hammering the front of the mag. So the crimp and/or compressed powder charge keeps the magazine from pusing the bullet into the case.

[BrownBear]

Worst case scenario in my experience are the rounds in the bottom of a tubular mag on a heavy recoiler- especially if you shoot a few, reload, shoot a few, reload, but never get to that last round. Without a great crimp, the long series of recoil slams can really shove that bullet down in the case. If you're not using a case full of powder, but are max at normal OAL, the greatly deeper bullet seating can really zoom the pressures.

Along with crimp, have a hard look at expander ball diameter relative to bullet diameter, especially on rounds that won't be crimped. Often a good tight neck plus a moderate crimp will prolong case life, compared simply stomping on a heavy crimp.

[Daveintheburbs]

Thanks Paul,

I have seen the battered bullet tips. Don’t think any of my loads have changed OAL as a result but as I said, I put a pretty healthy crimp on them.

Brown Bear,
I also load heavy 45-70 for my lever guns so I appreciate your comments. I also full length resize and trim by the batch when they get too long so I’m pretty conservative on case life, i.e. start with new frequently. As I said, absolute reliability trumps absolute accuracy for me.

[alaska bush man]

Lee Factory Crimp Die

Used them for years in my revolvers and levers! Great Crimp!