I just purchased a new 308 pistol barrel for my Savage 110 striker and had trouble finding the right brake thread.
I attempted to match it at the Hardware store and the auto store but no success. The gun store worker had to do some research but came up with 578 by 28 threads. The internet has adaptors to 5/8 by 24 and some brakes in 578 by 28. Wonder why Savage used the odd size?