Update. Put together my first rounds using 223 cases.
By way of background, the original load launched a 180 grain bullet from a straight wall case at about 1800 Fps. The only gun chambered was the winchester 1907, a pure blowback design. Intended as a deer gun, it saw some use by the French in WW1, was a favorite of gangsters and lawmen in the depression, and was used by police and corrections facilities.
Anyway, to make cases I used a harbor freight mini chopsaw to cut the 223 cases just behind the shoulder, trimmed to length, used redding dies to expand the case mouth and loaded 17 grains of IMR 4227 under a 180 grain graf bullet. Worked perfectly, ejecting and cycling the action without issue. Averaged about 1550 fps, which is fine. I was firing for function but accuracy looked promising.
My well worn 1907. It has a marbles tang sight and a fairly rare factory ten round magazine.
Attached FileOne of my 351 rounds along with its second cousin, the M1 carbine, and parent 223 case.
Attached File