Recently bought a new DPMS upper barrel assy, stainless steel, 1-8 twist.  Mounted it on a Bushy lower, excellent fit and function.  Set rear drum at 8/3 -1 ( got a good click on minus one setting ).  Set frontsight post base flush with top area of front sight assy.  Followed all break-in procedures, firing and cleaning without specific target.  Problem: shooting way high!  Rear sight is bottomed out and I have 10 clicks "down" on front sight post, still approx 8" over center of bull.  Front sight post is now above protective "ears" and not sturdy, close to coming out.  Totally unsat.  Any suggestions or experience in this?  Seem to me like I need to have the rear sight assy machined down to sit lower?  Thanks for any advice.