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Posted: 12/15/2006 12:32:34 PM EDT
| I am building my first AR and was wondering if these work with a removable carry handle? |
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Here's a brief history... In the begining, there were only A1's and A2's, no flattops. Then someone decided to cut off the carry handle and weld/screw a rail on the top of the receiver. This lead to a re-designed receiver with a flattop, quite similar to what we have today. Internet lore has it that Dick Swan (ARMS) poked a pencil through the top of the receiver at Colt one day and someone decided he made a good point and the receiver was too thin on top. At this point, the removable carry handle had also been dimensioned and worked out. They made the receiver 1mm taller (thicker on top). Instant problem: the rear sight is too tall. Easy solution: machine the FSB 1mm taller as well and mark an "F" on the side of it. The "F" stands for "flattop" Henceforth, we have two different standards on the height of the FSB. Now, there ARE military spec and commercial spec carry handles. Mil spec height carry handles align with "F" height front sight bases. Commercial spec carry handles align with A2 height front sight bases. Most flip-up rear sights are made for military rifles, hence they follow the military spec height. There is a special front sight POST that you can install in an A2 front sight base to get a military spec height rear sight to align properly. Almost all flattop receivers are made to the military spec height. The difference is always in the carry handle and front sight base. I don't have a list of makers that do it which way, but Colt and LMT will be all mil-spec. Bushmaster will be commercial. Not sure of Rock River, but I suspect them to also be commercial height as they do not offer "F" height front sight bases either. |
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Randall, I know you know better than that about the origin of .040 higher front sights on carbines, whether M4s, or the earlier types.  I can't comment on the pencil through the top part of what you posted, but you have to have known that carbines and SMGs built on the AR platform have ALWAYS had an .040 higher front post. Up until the advent of the M4, it was a higher post, and Colt still lists the higher post for their pre F marked base pieces in their parts list (part #SP64665). Best info I can get on the origin of the F base is that, when the Army decided to make the M4 the general issue weapon, they wanted Colt to provide weapons that used the same front post as the M16s that were still in use. This makes sense. My SP1 carbine came with a round front post in 1977 that was .040 higher than the rifle type, and all three of the short barrel pieces at my house (none of which have an F base) all need the .040 higher front point provided by the higher post. I do wish this fantasy about "F is for (Colt) flat tops only" would stop. It simply isn't true.  |
Actually, I don't "have to have known" about taller posts on carbines pre flattops. I'm admittedly NOT a colt historian. Why would carbines with an A2 receiver need a taller front sight post? |
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