View Full Version : Expanding 43 Mauser BELL cases

12-30-2015, 10:40 AM
I've got an old box of BELL 43 Mauser cases. They are about 0.5" longer than spec, which isn't an issue. However, the case mouth i.d. is about 0.375 compared to 0.43 with a new Bertram case. I've got the RCBS 3-die set. Will the expander die work to increase the diameter for the full length of the neck? I was hoping on getting some advice prior to shoving an expensive case into an expensive die.

12-30-2015, 12:45 PM
If it were me, I would find an intermediate expander to start with. Something about .400. So those cases are a half an inch longer than spec?

12-30-2015, 01:11 PM
Might consider gently annealing the brass before working it. If it's old, it might be brittle. Annealing is easy. Good information about it here on this site. Just have to look it up. Basically, heat the necks in a torch flame and remove from heat before it goes a dull cherry red.

12-30-2015, 03:29 PM
Are these cases marked 43 Mauser?

Don't know if the RCBS dies will expand the whole neck but the Lee die will. It uses a decapping/expanding rod just like a normal bottlenecked case. The problem is it does not leave a shoulder like the Lyman M die to stand the boolit on then seat it. I made a plug to go in the Lee Universal Expanding die for my die set.
You may want to do a chamber cast before you size the cases. The 71 has a different location on the case than a 71/84. The Lee die set is for the 71/84. Bore size is another issue as the 71 is supposed to be .446", mine is .457" but the largest boolit that fits in the chamber is .450". I do use 2400 powder behind the Lyman .446" and the Lee .450" boolits with 2 to 3 grains of poly-fil. The Lee boolit is the 300gr RFNGC for a 45 caliber revolver and shoots very well.

I use 400 degree heat paint I bought from a welding supply company and mark the shoulder of the case with it. When the paint turns color the neck is the right temperature to anneal the metal. This keeps from getting the metal too soft and collapsing when a boolit is seated.

12-30-2015, 08:11 PM
Needle nose plier's work

12-30-2015, 08:19 PM
Here it is. These are pretty old, crusty cases.

12-30-2015, 08:28 PM
The box was marked 43 Mauser, but the top part of the BELL sticker was gone.

The RCBS sizing die is shown in the attached photo:

01-03-2016, 12:54 PM
Appears you may need to trim the cases some before expanding due to the long neck. The die in the photo is just a decapper. There should be another die that just expands the neck like the pistol die sets have. I would leave the length a little long as they may shorten when fired.
You could try to fireform the cases using Cream of Wheat cereal, a fast powder and a wax plug to keep everything in the case before firing. Don't know what powders you have but something like Unique or 2400 should work. Do this after you have trimmed and expanded the neck.
To get the maximum life out of the cases just bump the shoulder back a couple of thousands to avoid overworking the brass.