This is the improved, inside lubricated version of the original .38 Colt Navy discussed below. The case is longer than the original to enclose the inside lubricated bullet, but the overall length is basically the same as the Navy version. The US Ordnance Office instructed Frankford Arsenal in June 1892 with loading of the .38 Long revolver cartridge although full production did not start until September 1892. It was used by all branches of service as the official U.S. service cartridge from 1892 to 1911. As a result of poor field performance, notably during the Philippine Insurrection of 1899 – 1902, the .38 Long Colt was replaced by the .45 Colt Revolver, albeit for a short period until the introduction of the M1911 45 ACP. (Erlmeier, Brandt Ref. 358)

The first loading had a tinned brass case without cannelure and was loaded with a 148gr. lead bullet. During the end of 1899 a case cannelure was added and in early 1900 tinning of cases were also stopped in favour of standard brass cases. Prior to November 1902 all Frankford Arsenal cases used the letter F only, afterward it was changed to F A.

Blanks were first used in December 1893 and original cases were unheadstamped. Later manufacture used existing cases, therefore the dates on these are not significant to the period used. The final blank used was adopted in 1909 with a necked case. Reject, second-class and fired cases were used and again the dates on these are not significant to the period.

APG was for Arsenal Principal De Guerra, Buenos Aires, Argentina. The P.C Co headstamp was by Peters as part of contract loading by the Ordnance Department.

During 1917 the production of 45 ACP pistols and ammunition could not keep up with demand and the 38 Long Colt was put back into service for National Guard use in the US and rear areas overseas. A contract was given to Remington in 1918 to produce ammunition for this use and cases were dated accordingly.