I was looking at Bushmaster and saw they suggested the additional purchase of the .040 front sight post for using the ARMS 40 mount.  Any reasons listed are appreciated, thanks.

because some of the front sight bases are shorter than others.



which would force you to back out the post to sight in and this is where the taller post comes in.

It comes down to this.  Due to the shorter sight radius of the carbines the front sight needs to be a bit higher to zero properly.

In SOME cases (not all) the tolorances stack up using the standard front sight base that the front sight pin may be on the verge of falling out when finally zeroed.  Having the taller pin means the base of the pin will stay firmly screwed into the Front Sight Base.

In my experience most carbines don't need the taller pin.

Note Colt has a Front Sight Base with a higher shelf so they can still use the standard A2 front sight pin and have the full range of adjustment.  All other manufactures use the standard A2 type front sight base, so some of their carbines will require the taller front sight pin.

That makes perfect sense to me guys, thanks for the heads up!

Is this info tacked anywhere? If not, it should be.