I have a 450 Bushmaster barrel and can't find a go gauge. I did pick up 2 boxes of ammo from cabelas and picked up a few pieces of new brass from a friend. Can I set the headspace to the factory loaded rounds, and then after I shoot them all, I will resize some brass and reset the headspace for my dies. I just haven't heard much mention about using a factory round to set headspace.

I figured I could add a piece of scotch tape to the factory round, set headspace, and then check with another piece of tape added. If anyone has any advise, let me know. I have set the headspace on all of my other barrels with resized brass. But I couldn't find brass in stock and did find a couple of boxes of ammo. I figured I could shoot them and then use the brass later.