This is not the normal type of part we offer at Charlie's, but have received a number of requests. This is a take-off from a new factory upper receiver group or rifle, so it has been test fired at the factory, but otherwise new. This is milspec standard height (F) front sight base and gas block, complete with sling loop (if desired) and bayonet lug. We have had a few requests to remove the sling loop (mostly from people who intend to mount an M4A1 side sling swivel inside the A-frame "F" height front sight base) so we now offer with or without the sling loop.
While basic, it is probably the best A2 FSB on the market. It is pined into the barrel, and to do this by the book, the gas block should be virgin (not drilled), and then mated to a new virgin barrel. This one has been removed from a barrel, which makes it delicate to install.
A note on "F" markings: Mostly, Colt has stopped marking the front sight posts with an "F", but this product is a "F height" FSB. The history behind the F is that when AR15s and M16s had the integrated A2 carry handle, the front sight was at standard height. During the advent of the A3 and M4 upper receivers, the height requirement of the FSB changed, ever so slightly. So, to differentiate between the older "standard height" sight base and the new height for "flat tops," the sight posts were marked with an F. Now that 99% of weapons using the FSB are flat top receivers, Colt has chosen to omit this step in the last few years, as just one more cost of operation. So, most Colt FSBs now will have no marking, while every now and then we see the marking. Either way, it is the same product, the "F height" FSB.
We recommend you use a gunsmith to install, as the drilling and reaming must be exact, and you need to keep the top at 12:00 dead center to match the gas tube hole. Also, the hole is tapered to match the taper pins (included) and is not a straight drill hole.
YOU MUST USE A VIRGIN BARREL, and not one which has taper pin holes drilled.
Colt
