Just a few observations about Oswald's revolver.
It was originally produced by Smith and Wesson in conjunction with the Lend Lease Act and designated as the “Victory” Military-Police (M&P) model .38, a variant of the long popular S&W Model 10. In accordance with the contract with the British, it was chambered in the British .38-200, which had a slightly large bullet diameter than the .38 Special the original Model 10 was chambered for. The bullet diameter was .361 inches as opposed to .357 inches for the .38 Special. The 200 was in reference to the bullet weight of 200 grains. Originally these were lead bullets, but in accordance with the Hague Convention, FMJ versions of the .38-200 were produced for use during WWII. A the end of the war, these handguns were returned to the US and were rechambered for .38 Special but the barrels still had a diameter of .361 inches while the .38 Special diameter was .357 inches. For this reason, that .004 inch difference between the bullet diameter and the barrel diameter prevented the bullets Oswald fired into J. D. Tippit from making consistent markings on the bullet and therefore could not be positively matched to the revolver. However, the firing pin did make a consistent mark on the shells which allowed the shells Oswald discarded as he left the scene of the shooting to be positively matched to the revolver which Oswald had in his possession when arrested a short time later.
