Taper crimping 9mm

[Scott]

I decided to start a new thread rather than continue posting in my other one.

So, I was having problems with my bullets being pushed into the casings with my last batch of 9mm. If you held the round between your finger and thumb and squeezed tight enough, it would make a small pop and the bullet would fall completely into the casing.

Someone mentioned that I needed to crimp the casing around the bullet, which I have been trying to figure out. I followed RCBS's directions to the "T" and found that I could still push the bullet in, so I tightened the die down a little more than another 1/8th turn. I can no longer push the bullet in, but I can spin the bullet while it's seated. I pulled the round apart and can see an indention where the crimp definitely took place.

I tried to tighten the die down some more to take out the spin, but I'm concerned with makng it too tight. In addition, once I get to another 1/4 turn in, the bullet starts to get deformed.

I'm using hard cast lead bullets that have a brass jacket over it made be Xtreme (bulk box bought at SW).

My question is: Is it safe to shoot a round like this?

I'm wondering if it's just the material that the bullet is made out of that causes the bullet to spin after being tapered crimped. Thoughts?

[MuzzleFlash]

First off, it doesn't sound right that the bullet can fit in the case loosely (the "popping" example you cited). A 9mm round should measure .355 and the case mouth should have to be slightly belled to accept the bullet. The case walls ID should measure about .353 after sizing. The bullet itself should have a good friction fit to the case walls before any crimp is applied. Perhaps the case walls are exceedingly thinned. Perhaps the pressure you're applying to form the crimp is excessive and is causing the case wall to expand like a baloon. This is easy enough to check. Your case diameter midway between the rim and the mouth should not change during the seating/crimp process. So take before and after measurements.

A consistent crimp is a good thing. It tends to provide more uniform starting pressure. You may want to invest a small sum in a Lee factory crimp die. These dies work very differently than the roll or taper crimp seating die. The "factory crimp" is much more like what you will find on commercial ammo. If you go this route, you'll actually back off the seating die so that it applies no crimp at all.

[Scott]

I'll go measure some of my brass and the bullets in a minute.

What exactly is a factory crimp as opposed to a taper crimp?

[Hoser]

A taper crimp just lightly crimps the case into the bullet. A roll crimp is designed for bullets with a crimping grove like found in some/most revolver calibers.

A "Factory Crimp" is just a name Lee gave to their crimp dies. They work ok, but I dont care for how herky jerky they make my press feel. Some swear by them...

You dont want to crimp plated bullets too much as you can score the jacket to the point where is seperates when fired. Consider just getting actual jacketed bullets. They arent that much more when you buy them in bulk. About $45 per thou delivered for 9mm.