Keep meaning to revisit and edit this...

I said "big bore" a few times. Meant to say "magnum."

The brake is three-port .30 cal brake (meant for the more powerful magnums) not a "big bore" brake.

And Ps.
The brake is really well designed and manufactured and I'd highly recommend it to anyone looking for a good muzzle brake for just about any caliber (he makes them in 2, 3 and 4 port).
And more specifically, the rear blast is managed very nicely with my 300 win -- I can shoot round after round and not get blurry-eyed and head-smacked; most of the blast is directed to the sides. And it dissipates so well, it's not a dirt-kicker either. (You would not want to be standing directly to the side when the rifle is fired, but it's tame enough I can bench shoot with someone in the next stall without him/ her wanting to slit my throat after just a few rounds).

Gary