The range wheel on a detachable carry handle has different markings for range, thus a different number of clicks, than the wheel on an M16A2.

The XM4 and the M4 (before they went flat-top) had the same upper as an M16A2, but did they have the same wheel as is later used in the detachable carry handle?

Thanks in advance.

IIRC, the early M4s used the standard A2 upper reciever, with the standard A2 rear sight assy parts.

The detachable carry handle uses a different elevation setting because there is not as much space for adjustment as in A2 upper.

Took some measurements, just for fun.

Colt detachable carry handle.  One full rotation is 24 clicks, 0.0760"; this is marked for 600m.  Approx 0.0032" per click.

Del-Ton A2 upper.  One full rotation is 25 clicks, 0.1575"; this is marked for 800m.  Approx 0.0063" per click.  600m mark is 12 clicks, 0.0756".

I think it's interesting that the sight which is more travel limited takes twice as many clicks to get the same distance on the sight.

I would think thats because its used in conjunction with the higher F marked FSB on both Carbines and rifles.