Making it law is.
You do you, let me do me. Okay? I want every less reason possible for the government to decide they can harass, interfere, arrest, or criminally charge me for anything I do that does not affect anyone else. If you pick up a firearm that you do not know what it is chambered in, take it to a gunsmith to have that determined unless you're capable of it yourself; this was one of the lessons you should have been taught right after being shown how to prove a firearm was safely unloaded.
Get your government out of my bedroom and my gun safe. Which are mostly the same thing.
Otherwise the next gun grab will be that anything that is not clearly marked of the correct cartridge is a prohib. 95% of milsurps will be prohib over night. Half the older SxS shotguns, drillings, etc same thing. 22 that doesn't indicate it can chamber S, L, and LR? Prohib. Marked 45 LC but it will fit a 410 shot shell? Sounds like a prohib to me. 5.56 NATO or 223 Rem? Well, if it isn't clear it must be a prohib!
F off. You give them a legal inch and they will take a mile worth of regulation.
In Europe, it's law that your gun has to pass a government proof and be stamped in the interest of safety.
Grizz