The original .38 LC was loaded with a "heel base" bullet which was .375 diameter outside the case, but .357 or so inside. Looked like an oversize .22 shell. The Army changed to using a hollow base, but I believe the Navy didn't change. From what I can find on the net, about 1903 or 4, Colt barrels were changed from .375 groove diameter to the smaller diameter. I know on my 1892, it has the larger bore, and a .358 bullet will drop right through. What I don't know, since the army already used the smaller diameter bullet anyway, and S&W started making 38 Special in 1899, and .38 S&W for years before that, did they just use the .361 bore?