I'm New To Reloading, Can Anyone Help?the Subject Of Crimping Confuses Me. Some Say You Don't Need To Some Do?. What Happens If I Choose Not To?.i'm Reloading .357mag And 9mm Auto.

[QUOTE=JOE LUKSIC]I'm New To Reloading, Can Anyone Help?the Subject Of Crimping Confuses Me. Some Say You Don't Need To Some Do?. What Happens If I Choose Not To?.i'm Reloading .357mag And 9mm Auto.[/QUOT


On the .357, want to use a roll crimp. As the revolver recoils, the bullets want to stay still, so a revovler can do a good imitation of an inertia bullet puller.

On teh 9mm, would look to a taper crimp. The force on a 9mm being rattled back and forth in the magazine, then slammed into the feeding ramp, are ones that would try to push the bullet back into the case. A taper crimp seems best for fighting those forces.

So in effect, are worried about opposites...in the revovler, the bullet si trying to jump crimp and work its way forward...in teh semi-auto, the ammo is slamed about and is trying to jam the bullet inward.

I use the Lee Factory Crimp die on everything but match rifle loads.

Thank You,ihave Hornaday Dies That Only Do One Kind Of Crimp.how Do I Know The Differance.

Revolver loads use a roll crimp in normal dies because the case headspaces on the rim and a good roll crimp holds a bullet very securely from movement, both in and out.
In a semi the case usually headspaces off the mouth of the case and if you use a roll crimp on them, you change the headspace which can lead to a misfire or increased pressures. So, on normal autoloader cases you use a taper crimp. The taper does not roll the front edge in which would change the headspace, it only tapes it slightly so the case can headspace on the mouth as it is suppose to while still offering some degree of prevention of bullet movement.
So, in short:
Revolver dies usually have a roll crimp.
Auto dies usually have a taper or no crimp.
If you have an expander button on you auto dies that is at least .003 inch smaller than the bullet diameter you will likely not need to crimp at all, at least not on rounds like the 9mm and .45.

Hornaday Dies Come With A Universal Seating And Crimping Die.what Kind Of Crimp Are They?

Standard dies come with a roll crimp, even for auto cartridges. Its best to crimp seperately from the seating operation. I like the Lee Factory crimp die because it also irons out any buldges in the case that might have popped up when seating the bullet. For the auto rounds you can use the roll crimp but only put enough crimp to just turn the case into the bullet a tiny bit. The seperate taper crimp is best but you can also overdo it.

What Ironhead said, ditto!

Standard dies come with a roll crimp, even for auto cartridges. Its best to crimp seperately from the seating operation. I like the Lee Factory crimp die because it also irons out any buldges in the case that might have popped up when seating the bullet. For the auto rounds you can use the roll crimp but only put enough crimp to just turn the case into the bullet a tiny bit. The seperate taper crimp is best but you can also overdo it.

Thanks For Your Help I Gave It A Trie And They Look Great.