Hi all, I'm thinking of fireforming some rimmed 50BMG cases in my regular 12ga shotgun. I'm thinking of 20-30gns 2400 with a felt wad, then cereal filler after annealing the neck and sholder.

This will be for a rifled 12bore falling block slug gun.
Thoughts on fireform charge?

NOt sure but I don't think a standard 12ga. could handle the pressure needed to fire form brass of that size.

Personally, I wouldn't attempt it until you talk to a good gunsmith familiar with what you are trying to do.

Have you thought about this way?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3667755792&category=31824

I am interested too, I have a bolt action slug gun that I am wanting to make a bit more accurate, thinking about going the brass shell route with a .735 slug.

I think a fireforming charge might be a little tricky with a large straight wall case, I would be tempted to make up an expander plug and go about it that way. I am no expert by any means but my tactical 20 takes a suprisingly stiff charge to fireform, and maybe I'm wrong but man, thick brass in a 3/4" straight wall case....

How are the guys doing it who were turning down the rims?

Ya, I've got a couple of box's of those, but they are only 2 3/4" long. That guy paid too much BTW as you can get them from old western scrounger for around $25 a box.

Ed has been turning off the rim and threading then makeing a brass washer and threading it also, then screw on the base of the BMG case, tourqe down and turn down to 12ga rim dimensions. I'm planning on staying at much lower pressures wo I think I'll solder the washer on then turn it down and put a bushing in to use 209 shotshell primers instead of the BMG primers.

www.mountainmolds.com is looking at makeing 12ga slug molds. I looked at some cast slugs in 70 cal and 12ga the other day and they look real nice. I know that he made a couple of test molds, but don't know if he is ready to sell them or not. If your interested you might drop him an email.

I was thinking that if I annealed the neck and sholder that it wouldn't take as much pressure to blow the case out with a cereal filler over the powder charge.

If you anneal it, you can fireform it fine.I use expanders,
the same ones I make my 700HE with, plus one extra.Just
have the setup handy, so that is what I use. Rob I think fireforms them.We both screw on the rims and I set them with
loctite.Ed.

what size threads do you use? I bought a 5/8 fine thread tap for my round bar, then turned and threaded the base on the lathe but it didn't turn out as nice as I would have liked. Maybe I just need to practice more? I was also wondering if an expander ball could push the case out enough to work in a 10ga?