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Posted: 1/12/2008 12:06:58 PM EDT
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I have a Colt LW upper with an F marked sight base. It has a taller post than my Bushmaster factory M4A3 upper. Is this correct or what. Chris |
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I always thought the taller front post meant for the barrels & flattop receivers compatability. If I am wrong let me know. I just received a Colt L\W upper with an A2 receiver and the taller post cranked all the way down. Is this a parts upper or was this barrel meant for a flattop receiver? dcobra23 
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Doesn't have a damn thing to do with flat top vs solid top. That bit of internet rumor, bought into by all kinds of folks who should know bwtter is like a case of atheletes foot that just won't go away.  Colt carbines have ALWAYS had an .04 higher front sight point; all the way back to the XM177s of the Viet Nam War. Prior to the advent of the M4, Colt used the .04 higher front sight blade. My SP1 carbine came with one in 1977. When the Army went to the M4 flat top as the standard infantry unit weapon, the F base was born, to keep Ordnance repair shops from having to keep two different height blades in stock. More recently, Colt (and now FN) are putting the F base on all production; because, as you've noticed, it's easy enough to crank the blade down on a rifle, which doesn't need the higher sight point. Again, it's an inventory reduction device. Colt has probably used up all the pre F bases they had, and so they're putting the F base on everything. Don't mean a thing, not a thing. 
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