I have one box of bertram, but would like to have other options and also form my own. Any ideas?

Not a heck of a lot of ways to get to that huge case, but at least Buffalo Arms has more Bertram in stock. Here's a LINK.

Thanks Bpesteve. I wish cases could be formed from a basic case, .577 nitro is too large at the base I guess and only 3" long, unless you could find 3 1/4".

577/500 is the parent case of the 505 gibbs, and has a different rim diameter and thickness than a 577 express or NE ... i built the 550 flanged from improved 577/500

cut the case web straight, cut a rim/extractor grove, and shorten, you have a 505 gibbs .. the case makers use the same first couple steps to form 577/500 as 505 gibbs

bertram is the only reliable source -

I was lucky enough to come into a good number of Bertram 577/500 basic brass a while back.
I made some No.2 out of some but don't want to use it up as I also want a 3-1/8" some day.
The unformed brass tends to be less expensive than formed and I also happen to have a set of forming dies although I am not sure if the case taper will allow the 3-1/8" to be made by simply backing off the dies.
Any idea if long 24ga brass will work? Maybe Magtech will sell some longer basic brass.