I've got a Thunderbeast 338 SR, a 5/8-24, and a 3/4-24 brake (I think this is the other one, I will confirm). I bought it to use on my 338 Lapua and the smaller brake to try and shoot it on my 6.5 creed.
I've not shot it with the 338, and have 50 rounds of 6.5 through it. Selling to fund...