Don't even try it. Firstly, it does need to be precisely aligned for it work without going off like a grenade and injuring you.
Second problem is that the Mosin's 7.62x54mmR cartridge is delivering roughly twice the power of its little brother 7.62x39mm. When the force of it hits the brake, it will shear the little screws off and send your muzzle brake sailing 50 yards downrange. If you are going to 'brake a Mosin, it has to be threaded.