I got a Krieger unused barrel, chambered in 300WM, threaded, and with a black finish for $103 on Ebay... Someone put $450 into it and gave up.. it has 1/2-24 threads on the muzzle.
No brakes have that thread. They are all 1/2-28 or 5/8-24
Possibly done by some machinist or back room gunsmith with no idea what threads are standard. Just have it cut back and re-threaded, shouldn't cost too much with a decent smith.
I can't tell if the original post was a serious question or not. Sure looks like somebody was halfway through with making some muzzle brakes.
