As I dip my toes into the world AK after being an FAL man for so many years...
I find there's nothing quite so polarizing as what one hangs on the M14x1 LH at the end of the barrel.
Without getting too far into the debate, something that comes up often is the efficacy of the slant-brake.
Some say it works, some say it's useless.
But I say it's two things.
First, it's iconic. AK's were issued with them and I expect to see one on an AKM variant.
Second, it's a banned feature unlike a plain muzzle nut. This despite being thought of as a brake not a flash-hider by most shooters.
I don't have enough 7.62x39mm trigger time to say if it works.
It could be that it really only works for full-auto fire, and is thus useless in semi.