From the rear of the Colt carrier to the front of the cut is .387". I cant give you a meaninginful measurement of the bottem front of the carrier to the front of the cut as it is longer than my 6" calipers. The semi cut section is about .008" taller than the rest of section that was removed forward of where the m16 cut had stopped. Hope this is of some help. I think thats my only colt carrier, but I'll look later and post any other colt carriers I have. I have seen some of the colt carriers where the entire bottem section was milled off so that the back of the carrier looked like a "C" on its side.
EDIT: I didn't have another colt carrier, but the FN ones I have measure .401" for the same measurement.