You need to find a firearms instructor.
Colt 1911 .45 serial # 171885 was manufactured in 1917.
The Colt 1911 was designed in 1897 and adopted by the US Army in 1911.
Call Colt
Good pistol
The Colt government 1911 .45 with that serial number was made in 1944 by Remington Rand
That Colt .45 government model was made in 1918.
Colt 1911
the judge fires 45 colt which is the same as 45 long colt not to be confused with 45 acp it also fires 410 shot shells
made by Colt 1918....................
45 ACP
Your colt model 1911 commercial (that is what the C stands for ahead of the serial number) was made by colt in 1917.
Actually, the cartridges are .45 ACP (automatic Colt Pistol) and .45 Colt (the cowboy era revolver cartridge. There is not really a Colt 45 Long. Can a revolver shoot both? Some can- they are chambered for the Colt .45 -but to shoot .45 ACP they need a "half moon clip"- a strip of metal that holds 3 of the shorter .45 ACP cartridges. 2 of those fill a 6 shot revolver. The PISTOL (not revolver) that shoots the .45 ACP cannot shoot the .45 Colt- no groove for the extractor to pull a fired cartridge out of the chamber, and it is too long.