Doogledog
Member
What is the difference in height of the standard A2 front sight base and the F marked front sight base for AR-15's? Can I use an F marked front sight on an A2?
A2 and F marked front sight base?
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Rubber_Duck
Member
F-marked is 0.040" taller. F-marked is for rifles with flat-top uppers/removable carry handles. So M16A2=non F-marked, M16A4=F-marked.
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Quentin
Member
Rubber_Duck is right on.
Are you asking if you can put the F-marked FSB (or a barrel with that FSB) on an A2 upper? Yes but zeroing you'll have to crank down the front sight to account for the extra 0.04" height. If you don't like the look of the sight way down in the well you might find a shorter post or file off a little from yours.
OP
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Doogledog
Member
Yea. I've got an old Pacific West Arms A2, and while I was still learning and stupid, I cut off the front sight post and replaced the upper with an A3 type. Now I'd like to put it back to it's original configuration but the front sight bases I can find don't have the holes for the taper pins in the same place. I thought I'd buy a new one and take the remnants of the original to a machine shop to drill the holes so it will match. Parts are pretty scarce but I have a spare F marked sight base so I thought I'd give it a try.
Taper pinned front sight bases and barrels are mated for life. Once you jack up a front sight base, it's impractical or impossible to try to replace it with another. Your best option now is to just hold what you have, or use a clamp on gas block/front sight.
madcratebuilder
Member
If you need the .040 taller FSB you can get just a .040 taller sight post. Bushmaster has them.
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