Help with .50bmg barrel fitting

[Mike4764]

This is my first barrel install by myself. Its a .50 bmg State Arms shell holder action. How much clearance between the bolt face and the face of the barrel shank? Do I take a measurement from the receiver face down to the bolt then cut the barrel shoulder? How would you measure it after its done? Im after benchrest accuracy.
Please bear with me this is a learning experience of the vary expensive kind!

 

[PEI Rob]

How much clearance between the bolt face and the face of the barrel shank?

.007" - .010" is fine. Lots of guys go for .005" but I can tell you it doesn't take much powder residue to close that gap. Nothing wrong with .007", in the middle of where it should be with room for error and it isn't an accuracy issue at all.

Do I take a measurement from the receiver face down to the bolt then cut the barrel shoulder?

I always measure carefully to get close but never rely on it for a final measurement.

How would you measure it after its done?

I headspace by threading on the action by hand and checking with a headspace gauge, trimming the shoulder back as required. I use sticky tape on the headspace gauge so its .002" thicker when doing this. When the barrel is torqued on the action properly, the headspace gets tighter by a thou or two. Unless your using a barrel nut then it grows by a couple of thou.
A 50bmg is a freaking big hole, I suggest you pre drill. I didn't pre drill my first 50 and it took a looooong time to chamber.

Do some searching, there is a WHACK of chambering info here.

Cheers