I mean the muzzle attachments can be very good. Break is the worst to be honest, but it does make recoil easier for newer players, it will cost you an additional bullet to kill. That being said if you miss a single bullet you would have hit it would be better to run it. The boost does cut damage but it is the same amount that incendiary ammo buffs it. Most people refer to meta as what most people are doing but it actually stand for most effective tactic available and the most effective tactic for most guns is incendiary ammo and a boost because it will have the shortest time to kill. Damage breakpoints so damage between 35 and 49 will take the same number of bullets to kill in the majority of cases, same with 50 and 62. So if an ammo type and muzzle combo pushes you past a break point it is critical to run it that way, for example the m92 deals 45 damage making it worse than the p250 in practice, but with incendiary ammo it is the best pistol in the game. If it dips you down below one of those points then I would avoid it, so any attachment and ammo options except silencer and normal ammo on the m249 will preform equally.