Yes, but they use a rod cut to the exact length then run a scraper like tool over the muzzle. If the scraper catches on the rod, it’s too short and you’re in deep shit.
I’ve heard stories of guys having barrels at exactly 16", and them getting a little damage on the end(nicks or scratches) that they lightly filed clean again. Barrel was then found to be too short as the scraper caught by a few thou.
I can do this for you the right way Dave for a minor fee($35 cut, chamfered, and polished), or if you want to retain the front sight post for a little more ($65). Up to you sir, just let me know if you want me to do it.