I wouldn't worry about this point too much. In fact, not at all.
The only way "another gun in criminal hands" has any rhetorical value is because of people who do not or will not own a gun for self-defense. If everybody had guns, nobody would care about another one in criminal hands.
Separately, "gun on the street" is an anti-gunner phrase. Its designed to be completely vague while also sounding alarming. The vagueness helps keep you from spotting its lie. Anti-gunner scare tactic. I have never, ever seen a gun on a street. They're not lying around in the gutters. They are always in somebody's holster, hand, pocket, or waistband.
And, while guns are out there in criminal hands, the number of bad guys with guns is far outweighed by good guys with guns. So, its not like there are all that many "guns on the street" even in the anti-gunners intended message.
So, I try to avoid using that anti-gunner phrase in order to deny it validity from repeated use. Besides, no sense letting the idiot opposition control the debate by using their language.