Almost Some,Kinda,Maybe......Well ???
Some device at the end of the bbl ???
Muzzle brake ?? Expansion chamber ?? Whatever you call it or it is called by the manufacturer,some help(in certain ways),others do not. This.....IMO only.
They all redirect the expanding gasses that are behind the bullet,pushing it(accelerating it)down the bbl. In what direction,how much,and the amount, will vary depending on the brake.
The very best brake that I have ever seen is the JP Brake. It looks almost identical to the "brake" on a tank. I suppose for a good/great reason. IT WORKS !! I have one on my 24" AR and it shoots like a .204. I once hit a yote 3 times before he could hit the ground(@125yds). The brake on my Weatherby Accumark(.30-378)makes it feel like a .30-06 at the most. The brake("Expansion Chamber") on my Taurus 6" .454 Casull reduces the recoil and muzzle rise to the equivelent of my Super Blackhawk(44mag) shooting mid sized bullets.
Some muzzle brakes are simply a POS and do not do a thing for both felt recoil and muzzle rise. Manufacturers discovered that by simply drilling holes at the end of bbl's, sold a ton of guns. ALL muzzle barakes are LOUD !! I could list the ones that fit into the above category but it would surely start a tongue fight.
Soooooo.....to answer the rather simple question of the OP,I would say..........depends. Depends on the shooter. Remember also that some muzzle brakes also add length and weight to the bbl. They WILL change the bbl's harmonics also. Some for the better,some for the worst. Also the tightness of the screw on brake can actually constrict the bbl to a certain degree and change the shot grouping.
Thinking about a brake,either after market,or already installed on a weapon.......do your homework,talk to owners of the brake,shoot them if possible. There are goods and bads to every brake. My JP is just plane "fuglie",but she sure does a good job.-----pruhdlr