Need help loading 175gr hpbt for AR10

[powerstroke79]

Need some help. Try to develop a load for a 18 inch AR10 using Sierra 175gr hpbt. Powders I'm using are IMR 4064 and Reloader 15. After hours of the great Internet and looking through a couple mauals I have, I'm more confused then when I started. Most loads I found look to be for a bolt gun and not a gas gun. My other confusion is the nato brass to commercial brass.

So some questions I have are
1 Do you guys back down loads for gas guns? If so 1 or 2 gr?
2 Nato brass down load 1 or 2 gr?
3 Do you make 1 load for nato brass and another for commercial brass?
4 If you down load for a gas gun do you also need to down load for nato brass

Like I said more confused then when I started.
Thanks for the help