Bill,
I watch part of your video. I sort of chuckled when I got to the buttcap part. That cast buttcap you show is (I think) the same one that I started out with. But I needed to bend that tail up a bit more. I heated it and on the first whack, it simply cracked.
So, then I had a buttcap model to use when I made my cap from .080 sheet brass. You may want to give this a try....then again....maybe not. The buttcap in the pic below I shaped from sheet brass. This one was my second attempt as the first one I beat the brass at the cap bottom (or top depending on which way you look at it) so thin that it just buckled on the install.
Anyway, if you want I could post the steps. I will warn you that this style of buttcap is "deep". Those are harder to form. Other pistol buttcaps are more shallow and far easier to make.
PS..I also made the TG via silver soldering three separate pieces of brass together. The TG was not in final finish in the pic.
FWIW
