450 Bushmaster headspacing?

[BoilerUP]

Close to pulling the trigger on a 450 Bushmaster prefit...

How does the 450B headspace in a Savage? I can source a piece of brass fired through a Bushmaster AR upper, or fired/FL sized piece...but haven't had luck finding a Go-Gauge so far.

Any insight from those who have previously built Thumpers would be appreciated...thanks!

[bootsmcguire]

I used brass for mine and works great. Be sure the brass you use is trimmed to proper length, the case mouth is your point of headspace and a stretched case or a case trimmed too short will change your headspace.