why do we need to crimp??

[statb]

Why do we need to crimp?
Do you need to crimp lead 40?
My Lee 4 set dies do not seems to like to crimp lead bullets

[joelogic]

Here, I googled it for you. Next time you can do it yourself.

I crimp my handgun ammo. Especially when loading lead bullets. Lead bullets are 0.001 larger than FMJ bullets and won't push the mouth of the case larger to accommodate their larger size. Instead, you will get some lead shavings and that will ruin your shooting day. In order to get around this, you need to use the expander die. But that makes the mouth of the case flare out beyond spec. Thus you will need the crimp to return the mouth of the case back to spec.

When using lead bullets, you will want to have separate seating and crimping dies. If you are using too much crimp and seating and crimping at the same time, you might accidentally crimp the mouth into the bullet too much and cause out of spec rounds.

tl:dr just crimp enough to remove the mouth flare.

As for lead in a CZ, you'll be fine. It has the normal lands and grooves rifling and a nice supported barrel. I've shot over 3000 lead bullets down my SP-01 and it's not missed a tick.

[bohoki]

generally my seat die shrinks the bell of the case enough to fit in all but the tighest chambers

but i did load some 45 and a certain swc bullet seemed to make me crimp (size down the front a bit) to me crimp is too strong of a word for what it did it was the taper crimp i guess

[30Cal]

I generally use none or just remove any bell I put on the case mouth.

Revolver and leveraction loads get a roll crimp.


The extra crimp die is relatively new to handloading. They've been around maybe only 15-20years. Before then the options were roll-crimp by threading down the seater die or none.

[statb]

Thanks for the help, I will remember google

[cassius]

You need crimp to prevent bullet setback on semi-auto pistols, from the rounds striking the feedramp.
And a taper crimp in that situation, as the rounds headspace on the case mouth.

You need a crimp on revolver rounds to keep bullets from slipping forward under recoil and mipeding the rotation of the cylinder. Roll or taper will do.

You need a crimp on tube-fed firearms to once again prevent setback, this time from other rounds stacked nose to tail, under repeated recoil.

And seperate crimp dies have been around for a lot longer than 15-20yrs.

[30Cal]

I managed to keep several semi-autos running for many many years without ever touching a taper crimp die, and without a lot of fuss. Hence I believe it is not a requirement. Maybe there are fussy automatics that need it.

To my recollection, Lee was the first one to sell a die set that had a seperate crimp die and that was late 80's early 90's.

[Beelzy]

To my recollection, Lee was the first one to sell a die set that had a seperate crimp die and that was late 80's early 90's.

Yep, it was called the "Factory Crimp Die"......what a joke.

However, what that die did to case mouths was NOT!

The only rounds I crimp are revolver loads, roll crimp baby.