Curious question

[Mil Dot]

Yesterday a guy was talking about a putting a muzzle brake on his 300 Weatherby. I said Vais makes a good brake and it really helps with recoil, but is pretty loud. His response was he wasn't concerned with the recoil but that it would add velocity. I don't quite know how it would but thought I'd throw it out for fodder.
Is this possible or proven?

He was talking 200 - 300 fps.

In reviewing the reloading manuals I guess I could just loan him the 338 RUM it'll push a 180gr bullet that much faster than a 300 Weatherby !