Optimum BUIS placement?

[Kram12085]

How much does placement of the rear BUIS on the rail affect shot placement? I went to zero my M4-gery (BUIS on the last rail notch) yesterday and my shots were consistently high. They were still noticeably high even after adjusting the front sight until it was nearly screwing out of the gas block.

[double_action]

Do you have an "F" marked front sight?

[Kram12085]

Not that I know of. What does that indicate and where would it typically be marked?

[double_action]

F marked front sights are taller that non f marked sights. They are used with flat-top uppers.

Here's where it's marked:



Here are the differences:




This thread explains the differences:

http://www.m4carbine.net/showthread.php?p=464465

[shark92651]

How much does placement of the rear BUIS on the rail affect shot placement? I went to zero my M4-gery (BUIS on the last rail notch) yesterday and my shots were consistently high. They were still noticeably high even after adjusting the front sight until it was nearly screwing out of the gas block.

At what distance were you zeroing?

[Kram12085]

double_action: Thanks for the comprehensive reply. I checked again to make sure and lo and behold, it's marked "F01". Although I'm slightly confused why you'd need a taller sight post if the "F" marked FSB is taller. Wouldn't you need a shorter post to compensate for the extra height and match up with a standard FSB?

I was trying to hit clays at 100 yds before zeroing on paper. I couldn't even hit the clays, the bullets were hitting significantly high. Thanks for clearing up the confusion. I'll probably use the BUIS on my Spikes upper and use a eotech on this one.

[gemini1]

Have you considered changing the front sight post? If a shorter one would still not work (which I doubt) then you can file it down until you get the desired height to zero your rifle.

[railroader]

Taller front posts for $5. Mark

http://www.tech-sights.com/ Look under accessories for extended national match sight post.

[Kram12085]

Wow thanks. I'll keep that link. However, I was planning on getting a holographic sight anyway and my Spikes upper needs a rear sight, so I might see how the switch works out first.