They can stop a lot.
In fact, Ronny 'Bonzo' Reagan stopped guns from entering minority neighborhoods when he was governor of California while having the FBI flood them with heroin AT THE SAME TIME!
Same with Crack.
Notice how meth has not taken over big city slums like it has trailer parks yet Crack was the reverse? That was President Reagan's doing. The Crack, anyways. Had to get guns to the Ayatollah and the Contras because why again? That's right, because they lacked enough guns for their shooting needs because math sez if you ain't got it in your hands to shoot with, you ain't got it in your hands to shoot with. That's why Tim McVeigh didn't get to nuke anyone.
Oh, wait, the subject IS guns!
NYC, the biggest city in the USA, was the safest big city here for a few years running till 2020. Then the dunderheads let a ton of criminals out of prison because of Covid plus there was that stupid bail reform thingy starting at the beginning of the year too. And now it's a shooting zone.
Plus now the Supreeeeme Court is set to overturn a 1908 law limiting guns in NY, so stay tuned to see how the math works out on that one.