Sighting in new BCM 14.5 middy with LaRue BUIS...is this a problem?
Hey guys. I rarely post here as I'm basically a lurker taking in as much information as I can and learning as I go along, but I ran into an unusual situation today at the range and I'm curious to know if this is something to be concerned with or not.
Before I get into the issue...A while back I purchased a Magpul MBUS for my LE6920 as I had removed the carry handle in order to mount a RDS. Zero the MBUS at 50yds with the base of the front sight post flush with the top of the FSB. A couple windage adjustments and I was dead on without having to make any elevation changes. GTG.
A week ago...I got in a new BCM 14.5 mid-length upper. Now what I don't want to do, is move my red dot and MBUS from the Colt over to BCM since the 6920 is zero'd.
A year or so ago, I picked up a LaRue BUIS that I never really used...so I figured I would mount the LaRue to the BCM, zero it...and then whenever I can pickup another lower, I'll have another AR build to play with.
Here is the LaRue BUIS I'm referring too...
http://i53.photobucket.com/albums/g5...3/IMG_0374.jpg
Ok...start out with base of the front post flush with the FSB, rear aperture (small) centered. Take 5 shots at 50 yds. In the picture you can see the first group at the top right...then you can see the adjustments as I walked in my rounds to the center of the target.
http://i53.photobucket.com/albums/g5...3/IMG_0368.jpg
http://i53.photobucket.com/albums/g5...3/IMG_0367.jpg
Now...this is what has me at pause...
http://i53.photobucket.com/albums/g5...3/IMG_0372.jpg
My question is...is it normal for the front sight post to be this elevated after a 50 yd zero depending on what rear BUIS may be used? I was under the impression that rear sights be they folding or not...were supposed to be pretty close to the same height off the upper receiver...but I may be wrong. IDK.
Remember...the front post on my Colt needed no adjustment at all. It's still flush with the FSB and it's dead on at that same range.
What I may do, is mount the carry handle off the Colt onto the BCM and re-zero to see if there is a change.