crimp die for 12 gauge brass?

[Lefty Dude]

The Lee hand loader will roll the case mouths if you go far enough in the die. However an over-crimp is very possible.
I use this method, place the loader in a vise then use the plastic mallet to drive the case in the die. A plastic mallet and wooden dowel will remove the case. If you FUBAR, and put to much roll on the case mouth, the roll can be removed or adjusted by using a metal round mandrel or such and the plastic mallet. Place the case over the mandrel and carefully rotate the case while tapping gently on the roll.
I also use this method to repair a case that gets dented or heaven forbid, one gets stepped on in the heat of the battle.

A mandrel & plastic mallet is a Brass shot gun cartridge reloader/shooter best tools.

[Pappy Myles]

Ditto what Black Powder Burns said.

I have the RCBS 12 ga Cowboy die set,  Pricy.....  but I use the shell holder, and the crimp die to role crimp the brass.

[hydin]

I appreciate the advice on it, but I'm mainly looking to replicate a movie prop (or a box of them, actually). I wouldn't be able to really reuse the die since this is kind of a one time thing.

Still, if someone is looking to make a quick 20$ or so, I'll be more than happy to talk