Anyone know how the 38 cartridges[ 38 S&W- 38 special] got that designation when they are actually 35/36 caliber?
O.D. of the case - IIRC
It goes back to the heel type bullets that were basically the same diameter as the case. Like .22 rimfire are still today. The .36 cap and ball conversions used a .375 diameter heel base cartridge which Colt carried over into their revolvers. Like my .38 Colt. The .38 Short Colt used a heel type bullet of .375 diameter and the .38 Long Colt used a Hollow Base bullet up to .360 diameter. It was expected to obturate to fill into the rifling for accuracy. Later, they simply reduced the bore diameter to .357 and discontinued heel base bullets.
Ultimately, .38 is simply derived from rounding up .375 to .38.
Al
I picked up a bunch of cases at the range marked "38 AMU " , this was pre computer days and I couldn't figure out what they were ...the book had the answer.
Gary
One time I picked up a good double handful of 38 AMU brass. Had them for over a decade until I ran into a guy that had one of the pistols, he gladly traded me an original live round for the brass. He would have paid a lot more, but he needed them and I didn't.