"F" marked FSB, Quick questions...
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Maverick223
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I am far from an AR expert, but if you have problems (and you might because IIRC the F-type front sight is for flat-tops and carbines) you should be able to simply replace the sight post for a slightly taller one (there is only a few hundredths difference between the two). I'd try it and just order the approx. $5.00 part if it doesn't work.
I have a bushmaster with a non-F marked FSB. It has a detachable carry handle and is perfectly zeroed.
However, I'm not certain, but it seems to me that the carry handle rear sight elevation is matched to the FSB type... meaning that a non-F marked FSB needs a carry handle designed for that FSB and the F marked FSB would need the carry handle designed for the F marked FSB.
However, I'm not certain, but it seems to me that the carry handle rear sight elevation is matched to the FSB type... meaning that a non-F marked FSB needs a carry handle designed for that FSB and the F marked FSB would need the carry handle designed for the F marked FSB.
Quentin
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The answers above are correct. If you have the taller milspec F-marked FSB on a flat top then you should buy a milspec height rear sight or carry handle.
If your flat top has the shorter A2 height FSB you still should go with a milspec height rear sight or carry handle (for compatibility) and buy the Bushmaster 0.04" taller front sight post to bring the front sight up to milspec height.
I did this to my ArmaLite middy and it solved the problem nicely and permanently. The other option is buy a shorter commercial height rear sight or carry handle as mic_poo pointed out but you'd always have to worry about this when changing out the rear irons. Instead I'd go with the taller sight post as it's only $5.50 or so. One problem with this is on some FSBs the taller post sticks slightly above the protective ears. Don't know which brands are like that but it wasn't an issue with my ArmaLite.
Annoying problem you have to be aware of with ArmaLite, DPMS, Bushmaster and a few others. Technically Colt is to blame for this, they should have kept the A2 height FSB for flat tops and just shortened the rear sights to fit. Then it wouldn't matter which upper receiver a barrel/FSB is put on.
If your flat top has the shorter A2 height FSB you still should go with a milspec height rear sight or carry handle (for compatibility) and buy the Bushmaster 0.04" taller front sight post to bring the front sight up to milspec height.
I did this to my ArmaLite middy and it solved the problem nicely and permanently. The other option is buy a shorter commercial height rear sight or carry handle as mic_poo pointed out but you'd always have to worry about this when changing out the rear irons. Instead I'd go with the taller sight post as it's only $5.50 or so. One problem with this is on some FSBs the taller post sticks slightly above the protective ears. Don't know which brands are like that but it wasn't an issue with my ArmaLite.
Annoying problem you have to be aware of with ArmaLite, DPMS, Bushmaster and a few others. Technically Colt is to blame for this, they should have kept the A2 height FSB for flat tops and just shortened the rear sights to fit. Then it wouldn't matter which upper receiver a barrel/FSB is put on.
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So I bought a truglo night sight front post for the BM... it appears to be taller than my standard post. I haven't installed it yet, but I'm assuming I can adjust it all the way down to the level that my standard front sight post is now.... safe assumption?
Quentin
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It should screw down quite a bit. Its base may not be flush with the shelf on the FSB which shouldn't be a problem though, just cosmetic. The other way where the base is a lot higher than the shelf allows the post to flop around, affecting accuracy (which is the reason to buy BM's 0.04" taller post).
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