223 will chamber in a 204
Just cause it fits doesn't mean it's safe. That statement can be very very dangerous. But generally if it fits, extractor supports it well enough, firing pin is strong enough and the case doesn't move....it can fire even though it's not safe
I just googled .204 Ruger, and it is .204" 5.2 mm
How does a .223, 5.56 mm bullet fit ?????
CASE is SHORTER .....
I have personally seen a 9mm cartridge feed from a magazine into a .40 cal, fire, and hit the target. Obviously not good and a lot of circumstances can be downright dangerous! The 9mm casing expanded inside the .40 cal chamber to the size of a .40 for just that part of the cartridge!!