i recently had my Rem 700 XCR 300WM threaded cause I wanted a brake. I am a big guy, 6'5, 330lbs, and after shooting my 300WM 10 rounds, i would flinch some, and I never have flinched before and my groups would open up to 1.5", when shooting expensive 300WM that was unacceptable to me. I worked and worked tryikng to fix it, cut i just couldnt for some reason. So, even though I didnt want to, i got a brake put on. Shrewd is the brand I believe, and my first range trip, i couldnt believe 2 things. First, was how unbelievably loud it was. I dont know if it was because it was my first trip out with a brake or what, but the concussion it made was tremendous all around, a couple people around me even commented on how loud it was. Thankfully it was empty on a 20lane range. The 2nd thing i was amazed at was how much recoil it reduced. It was incredible. My pretty light weight 300WM that kicked like a mule I thought was now as easy to shoot as a 308. I could literally feel the brake working. I shot it 85 times that day, and my shoulder was perfect and I wasn't flinching.
I was torn though, I couldnt tell if I liked the rifle now. It was loud as a canon on steriods, but i could shoot it as much as I want. I really thought about selling it then and just concentrating on smaller stuff, like a ballistic match to the 300WM, a .260 Rem. I loaded up some more rounds, and went back to the range, and it was more busy, most benches were taken up, so i was nervous if I was going to bother other people. I set up, and started shooting. I dont know why, but I really didnt notice the increase in sound near as much this time, and no one around me really seemed bothered by it thankfully.
So i think shooting with a brake just takes some getting used to, but they serve a purpose. On a 308, I dont think there needed unless you are shooting long distance and need to see your shot splash. In that case, i think they do well, but ultimately not needed.