20" Upper+BUIS learning experience

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20" Upper+BUIS learning experience

Postby commander faschisto » Fri Aug 19, 2011 12:30 pm

OK, so...I'm finally getting around to doing a boresighting for the ridiculously expensive Bushy V-Match front flip-up iron sight I've had clamped onto the faux front "gas block" on my 20" upper. Stick boresight device in bore, look at target 25 yards away, and....no red dot anywhere in the vicinity of the entire target board! WTF? :(

After walking toward the target while holding on center, I finally see the red dot moving in from the far right side of the target board. Hmmm. How can this be? Even with the rear BUIS cranked all the way over, I still can't get the dot near the crosshairs on the front sight "reticle" (I hate front post sights...). It occurs to me that something is amiss here. I decide to take the viewpoint of the thing being aimed at, and center my eye in line with the barrel/flattop picture. Somehow, from the front of the rifle, it becomes obvious that the front BUIS is actually tilted a couple degrees to the left!

Checked the installation job on the front BUIS...tight and even. Light comes on! :idea: Much as it is hard to believe, the faux front gas block/sight base was not clocked to the 6 o'clock position when they installed it at the factory! I have to sit down due to the shock of this discovery.

Reinstalling said "front sight base" to the correct position miraculously solved all of the aforementioned sighting-in difficulties. Whoda thunkit? (that'd be a cool name for a rock band...)

Just thought I should pass this tidbit along to other 20" 450b owners as a "lesson learned".
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