AR Sponsor
Posted: 3/6/2010 12:08:36 PM EDT
| What does this mean? Is it a different height than an A-2? Please let me know... |
|
It is used to make up for the height of using a flat top upper. The 'F' marked front sight bases are .040 inches taller than the standard base.
If you mix a standard front sight base and flat top upper, you (most likely) can not get the front sight post adjusted tall enough to get a good zero,,,so the 'F' marked base helps out. Measurements from top center of barrel to top edge (flat) of front sight base Standard base = 1.94 inches 'F' marked base = 1.98 inches HTH |
|
I would agree with JCROWL that it is not needed on a 20" Flat Top. To get my BCM 20" to zero with a MATECH BUIS and the F FSB, the front sight post is actually adjusted way down. About .060" So it seems to me, the extra height on a F FSB really isn't needed on a 20" rifle. Carbines are different. I have had trouble zeroing flat top carbines with standard FSB's. Easy fix, just get the taller Front Sight Post.
I also have a FN 20" Flat top upper/barrel group that does not have a F marked FSB. So it looks like FN who makes the M16A4 doesn't even worry about it on their rifles. Quoted:
The sight base on which the front sight post is installed is just a tad higher than the A2. Designed for use on flattop carbines and rifles. From what I've read it's really not needed on a 20" flattop rifle. |
AR Sponsor