My Astra 400 takes 9mm Largo and 38 ACP rounds. The rimless 9mm Largo headspaces on the case mouth. The semi-rimmed 38 ACP headspaces on the rim.
My 1903 Colt Hammer takes semi-rimmed .38 ACP. It also takes the rimless 9mm Largo, which headspaces on the case mouth in the Colt. The 9mm Largo case is slightly longer than the 38 ACP, which brings the 9mm Largo primer to the exact height in the chamber as the 38 ACP.
3.2 grs Bullseye works perfectly in each, with a 125 gr cast bullet sized to .356". I use 38 ACP/Super dies for the Astra and the Colt.
New Starline 9mm Largo brass measures .898" in length. Vintage 9mm Largo brass that I have measures .911". I think the shorter Starline brass might cause headspacing problems as it seats lower (further) in the Colt chamber.
The Astra and the 1908 Colt .25 have the same PITA barrel/slide assembly. Colt had Astra make the later Cubs.
What's all this rambling mean? Not sure. Just trying to tie the Astra/Colt connection in the early 1900s and even later.