Nice move! 15/17 + 1 of 10mm will do the trick every time! The most flexible round out there, especially since you reload. You can make puddytat loads all the way up to bear stoppers, kinda like a 41 or 44 Magnum.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek