My son is going to Marine Boot Camp this summer. He joining the reserves.  I am putting an all Colt Flat Top upper with a 20" barrel for him as a present.   I have a Colt M4 carrying handle with the 6/3 elevation drum.  Can I use this M4 carrying handle on the upper receiver if I am using a 20" barrel with the standard A2 front sight?

Thanks

The Colt M4 handle is different (not the elev. wheel) than Colt's, and everybody else's A3/A4 handle.

The Colt M4 handle is different than Colt's? Now I'm really confused.  I believe the standard detachable handle is the same for all models, I could be wrong...

Thats what I am trying to find out.  I don't know if you can put a Colt M4 carrying handle on a standard Colt 20" flattop rifle.

It would be nice if there was complete verification on this issue.  From what I know, and I could be wrong, when colt builds a rifle with a flattop upper, the M4 front sight base is used along with the M4 carry handle, no matter what the barrel length is.  When the flattop concept was being developed, it was decided to make the sight plane higher, increasing the height of the carry handle and front sight.  As for the reasons for this I am not sure, maybe to give the elevation post in the handle more room to move, or make the carry handle opening larger so that you could still sort of use it.  Whatever the case, when the other manufacturers starting building rifles with flattops, they decided to just stay with the original front sight and design a lower carry handle.

I have two Colt flat top handles in front of me as I type. One is from my MT6400C (civy M4) while the other is off my MT6700 (Match Target Competition HBAR). They both measure the same in all dimensions!

I think that what you are talking about is that according to Bushmaster the "Colt A3 Removable Carry Handles are higher than mil. spec." (?) "and require this .040 taller Front Sight Post". P/N 9349056-M   $4.95
http://www.bushmaster.com

If the Colt M4 carbine handle and the handle from a standard Colt flattop rifle with a 20" barrel are the same dimensions, then I should be ok.

Thanks for the help!!!!

Not quite! As I understand it the Colt A3 and M4 use the same front sight bases, which are of a different height than the A2 front base.

So if you want to use the Colt A3 or M4 detachable carrying handle with an A2 front sight base you should youse the Bushmaster .040" taller front sight post to make up the differance.

As you presently stand, you would only be ok if you were using the Colt A3 or M4 frt sight bases with your detachable Colt handle!

I have a Colt M4 barrel that was taken from an older M4A2 carbine with the fixed handle.  I have since taken the barrel and put it on a Colt flattop receiver.  I was able to zero in the carbine ok using the Colt M4 detachable handle.   I measured the sight tower on the Colt M4 from the bottom of the lug to the top of the tower.  I found that it was the same height as the sight tower on a standard 20" A2 barrel that I have.  Has anyone out there actually measured the sight towers of the Colt M4 flattop and the standard Colt A2 and found a difference?  Is the sight tower on the Colt M4A2 different from the Colt M4 flattop?

From my quick and dirty measurement tonight, the "F" marked front sight tower (from my Colt 16" M4 barrel) is 0.050 in. higher than the sight tower from my Gov't A2 barrel. I measured from the top of the barrel to the "flat" where the sight post is mounted.  Hope this helps

Yes, that helps.  My measurements were crude.  A .05 of an inch difference in the sight tower may not be enough of a difference to prohibit the use of a Colt M4 handle on a Colt flattop rifle.

Thanks!