I just purchased an M4 A3 type upper and placed on a tactical type carring handle asseblies made by Rock River.  Using the A2 type sights I cannot Zero the weapon at 100 yds.  I have to almost unscrew the front sight completely out to hit the center area.  Is there sometime I'm missing or is a special front sight I needed if I'm going to using the standard sights.  I plan on purchasing a Reflex type sight, but till want to have the capability of using the standard sights.

Any help or advise appreciated.

John

Bushmaster sells a .040" taller front sight made for M4 uppers.  That ought to cure your problem.

Colt M4 barrels use a different front sight base than their "A3" carbine's and every other brands front sight base. As "Seth_Livzz" said, [url=bushmaster.com/shopping/scopes/9349056-m.asp]Bushmaster[/url] sells the correct front sight post to compensate.

Thanks for the advise, I just purchased one from Bushmaster.

Its great to have knowledgeable people on the board!!

Thanks!
John