Measure from the front surface of the cylinder to the muzzle.
The only 'dumb' questions are the ones not asked.
Kaaskop49
Shield 5103
While automatics are measured from the muzzle to the bolt face. Just thought that I’d mention it in case anyone was curious. Here’s another dumb question. If a chicken and a half lays an egg and a half in a day and a half how long will it take a rooster to hatch out a brass doorknob into a hardware store?