im not too sure about that Black Knight, i have a colt police positive spl. made in 1914 that will only accept 38 special ammo. i tried to drop 357 mags in the cyl. a minute ago and they dont fit. im not trying to sound like a know it all, just saying i dont see that as an issue. ill bet your friends gun was modified.
In actual fact many of the early .38 Long Colt revolvers WILL accept a .357 magnum round! But they were mostly made in the late 1880s and 1890s in a quick succession of models. Many being US Army issue. The very revolvers whose impotency led to the .45 ACP and the M1911.