montana muzzle brakes will give a 100 fps increase. I loaded identical loads in my 338/300 and one belonging to a friend(his had the Montana brake) and fired the different rifles over a chronograph the one with the Monmtana brake shoot 100 fps+ faster and this was out of a shorter barrel, hell I wouldn't have believed it If
we hadn't done the test!!!
I was checking a factory load over the Oehler 35P last fall in my 300wm and a buddy had his there too. Mine was a 700, his a Ruger 77 mk11. Both had 24" bbls and his shot 125 fps faster on average with the same factory box of ammo. This has been my experience with Rugers though, they seem to get a little better speed than the others for some reason... all else being the same. His wasn't a Ruger was it?
Theoretically, there is potential for some extra velocity, as some pressure is still behind the bullet even though the bore is larger in the brake and alot of pressure is vented off as it passes by the vents. The rifling is not slowing down the bullet any longer but, how much this ofsets the larger bore and progressive venting is anyones guess. A 100 fps gain in two or three inches of bbl is possible, but still a guess unless you remove it and then compare to yours. Did you remove it, and were they then both the same? Interesting.
That would be the best way to test this theory. Shoot it with the brake and then shoot it without. THE SAME RIFLE. I have done this and there was NO difference in velocity.
As mentioned, the bullet is not touching any steel as it passes through the break. Most brakes need .016" to .022" clearance around the bullet to work well.
Even though the brake may be 2 or 3" longer it is NOT the barrel with rifling in it.
We know that every barrel is different and as the cutter bores the barrel at the factory it wears and there is a slight difference in land depth as this happens. If someone gets a barrel when the cutter is about to be changed, the rifling will not be cut quite as deep as a new cutter will allow.
This is extreme but just a .0001" or .0002" could make a heck of a differance if it happened.
Just a thought.
My experiance is, there is no increase in velocity with a break on.
There may be a velocity gain but I'd bet the farm it's not 100fps or anywhere near. My gun w/wo brake makes no noticible difference in speed. I made a VERY tight brake for a 308 cal that was .315 ID and if it did help the velocity it make up for all that speed in accuracy. Shot terrible. I was told as Darryl says that .015 or so is the best number so I made a brake and tried it closer, .015 and opened up. I would say that .015 or more per side is fine.
Another side note. The effectiveness of a muzzle brake is inversly proportional to the bullet weight to powder charge weight. In other words, a 220 swift is the king of recoil reduction and an efficient round, like a 7 BR or a 300 savage will benifit far less. A WSM lets say, will benifit, but not as much as your 300 weatherby.
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!
Others may know more about this, but having talked to Kevin Knight at muzzlebrake.com , he indicates that his muzzlebrake can actually increase velocity. It is an extension to the barrel, trued and crowned.
I also think it is one of the better looking brakes as it is matched with the barrel. I really like the one he put on my gun. It is worth giving him a call.
I think others on this site either provide or have used others brakes, so hopefully not stepping on any toes.
In a world with lots of options, I have not heard of anyone using Magnaport in some time. I do not really like the looks of the large brake at the end of the barrel.