Why is it that important. I dont jump through too many hoops boresighting a ricle. I try to get the crosshairs lined up with the grids, and I'm on paper at 100 yards. I'd never use a bore sighter without sighting in the rifle afterwords.
I'f you're talking about mounting the scope. Just use a string leveler (without the string) to get the rifle level, then use it one the scope until you get 'er tightened down.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071