I've got a Bushmaster made 20" A4 style rifle, fitted with the factory carry handle and sights.
I took the rifle out a few days ago to check my zero using the 50 yard 6/3-4 "Marine Improved Battle Sight Zero" method.  By the time I was finished, I had rounds hitting about two inches high, an pretty much all of the base of the front sight post sitting above the top of the front sight base.

First of all, is this something that I should be concerned with, and second, do I need to be worried about getting an extended front sight post for the rifle now?

Nobody here knows how far these things can adjust before they fly out?

You apparently have a "non-F-marked" front sight base. The good news is that this can easily and cheaply be fixed.

Just go to the bushmaster website and order one of their "tall" front sight posts.

I'll find a link for you and post it in a few minutes.


Edited to add the link. http://www.bushmaster.com/products.asp?cat=21
Once you click on the link, scroll down just slightly to the first sight pin you see, which will be marked "A2 Front Sight Post for Flat-Top Colts" (part number 9349056-M). The picture will look just like the standard one below it, but in reality this post is 0.040" taller than the standard one, and it will fix your problem right up.

OK, great, thats kinda what I figured I would need to do...

Now, since I've got a non F-marked front sight base (And I just looked at it, can't find an "F" stamp anywhere), does this mean that I'll be pretty much screwed if I purchase a tritium front post and try to do the same zero?