>>64481639
It's a little different if you are talking about an open bolt SMG or LMG converted to closed bolt as opposed to something like an AK/AR/FAL. A semi auto AK is fine.
A closed bolt BREN for instance is pretty dumb but that's why they aren't very common. Most people recognize that and not many people are willing to buy one. They exist purely for the tiny handful of people who would put up with every issue that a closed bolt semi auto version would entail, in addition to the exorbitant cost because that's just what they want. It doesn't have to make sense.