Started working on the lower using some 6061 flat bar aluminum stock. I ran a face operation. I might drill the 1 and 3/16 inch hole in the center of the original stock point. Also got another piece of stock for the barrel and it’s much longer. I already have the buttoning tool and was thinking about lubing it and pressing it on a hydraulic press with some spacing rods. I have a blank piece for the upper that I’m going to use the negated details of on the bottom most portion to sit in line with the pin position of the lower.
The one on the right reminds me of the .499 Leitner-Wise project. Straight case, rebated rim. U.S.C.G. was looking at high powered boarding weapon that could use existing M16 lowers around 20(?) years ago. A 30 round GI m16 mag would hold 7 rounds of .499 if I remember correctly.
Project got shelved and there were uppers around. Ammo came from Silver State.