Hi. What is the difference between an F-marked base and one that isnt? I know they are for flattops but that is all I know. I just bought a new RRA CAR-15 A3 and it does not have an F mark on the FSB. Will this cause compatibility issues with anything?
Thanks,
Mike
You may have some zeroing issues using a non F FSB, Bushmaster makes a taller front sight post to remedy this is .020" or .030" taller.
I think the difference between the F and non-F FSB is something like the F is .040" taller. Colt developed the F FSB for use with A3 upper recievers. A problem may arise when trying to zero irons on an A3 with a non-F FSB. In order to achieve mechanical zero you could run out of elevation on the front sight post. As posted above, Bushmaster sells a taller front sight post to alleviate this.
Maybe RRA includes the taller sight post already?
Bullets do not develope their own lift… they start to fall towards earth the instant they leave the muzzle of the rifle – the ballistic arc that allows a rifle to shoot high at some point, is the result of the fact that the line of sight and the center of the bore get closer to each other at the business end.
Conversly, as you move aft, those lines get further apart and it is neccessary to elevate the front sight as it is moved back, to keep it in the “zero” line of sight.
Your rifle (although I am sure RRA never made an A3), most likely will have a tall front sight post installed, the best place to find out is at a range 