I’ve heard some speculation here that CMT makes uppers for Colt.  I had a chance to  study some CMT and Colt uppers to see if they appeared to be the same.

They are all recent production.  1 CMT flattop, no M4 cuts.  1 CMT flattop w/M4 cuts and 1 Colt A3, no M4 cuts.

They all work flawlessly and have the same color finish.  The machining on the CMT is marginally better as to tool marks in the Charging Handle cut, but this is pretty picky.  The Colt had a few small scratches/dings through the anodizing.  Looks like rough handling prior to packaging.

I have concluded that they are not made by the same CNC program.  I guess CMT could be making them for Colt, but they are not using the same tool paths and geometry that is used on the CMT receivers.  This is not to say that CMT never made them for Colt, just that these appear different.

I didn’t take any measurements, just observed the way some complex areas were machined.  The area on the right side between the ejection port and barrel threads was a good place to see subtle differences.  While they are very similar in many respects, it is clear that the tool paths are not the same.

Besides the fundamental differences in the machining, there were a few things noticeable on these particular parts.

The charging handle (Colt) snapped closed with a lot more positive feel than the 2 CMT’s.  Not a biggie.  They all work just fine.

Barrel alignment:  I have installed the same Colt 16” Lightweight barrel on all 3 receivers.  The first was the CMT W/O the feed ramps.  The rear sight was about pegged to the right to get on target.

I removed about .008 from the slot and it centered up fine.  Same story when I installed the barrel on the CMT with the M4 cuts.  At this point, I was convinced that Colt messed up the front sight installation.

Funny thing happened when I put the barrel on the Colt upper.  Near perfect alignment (4 clicks on an ARMS 40).  Now I’m thinking the CMT’s are a little off.  Far too small a sample to draw any conclusions and an easy fix in an case.

I like all of them and they all work good.  I’m certainly not starting a which one is best thread.  Just wanted to pass on some observations.  BTY, the CMT’s were less than $100 delivered and the Colt was about $140 (stripped) from Brownell’s.

Edit:  I forgot to mention that the "T" markings on the CMT seem to be a little bigger than the Colt.  Part of that may just be because the paint is applied outside of the lines on the CMT's.

Colt uppers are marked with the forgers identification, as are most others.


Mine was made by Cerro Forge, for Colt (hence the "c" and keyhole.)
Similar to the pic by CJan_NH below;

Yes, the Colt has the "C" and the Keyhole forge mark.  The CMT's have no forge mark, but the one with the M4 cuts has a small stamped "M4" centered above the cloverleaf.

A lot of claims are being made about who makes what for Colt, but without clear markings, no one really knows. It's mostly speculation.

Not sure if it's true, but I've heard CMT is now Colt's biggest outsourcer making pretty much everything but the barrel and the furniture. This does not mean all Colt's are made by CMT. I'm sure they have more than one source for parts.

All companies outsource from different people. Even Olympic gets their bolts from CMT. RRA also gets a large amount of parts from CMT. Keep in mind that different people will have different specifications, so they're not all the same.

AS has been said before, it's the Quality Control testing after the parts are purchased from the supplier that makes the difference. Certain Companies reject entire lots of parts, because of very strict testing standards, while other companies test the parts very little, if at all. I will not name names, as people tend to get up in arms when anyone suggests their rifle may not be the best, but you get the idea.

Exactly. All of those different companies that use CMT don't have the same standards. If you buy a CMT made Oly bolt assembly, that does not mean it has went through the same process as a Colt, or any other CMT made bolt.

Well. I got to thinking how I would outsource if I was Colt.  I would probably have the raw forgings (with the "C") delivered directly from my supplier.  That would insure the materials meet spec.

Then I would provide them a copy of the CNC programs to cut the part.  Death penalty, of course, for using the programs to cut other brand receivers.

Finishing and such ought to be pretty straight forward being farmed out to a Colt approved anodizer or done in house if capeable.

Follow up with proper QC on the finished parts and ya really can't tell it from an in house part.

This could explain how CMT could be making Colt uppers that are not machined exactly like the CMT uppers.  I guess we probably won't ever know for sure.