When did Colt change from gray over to black on the a2s? When were m4 cuts added? Does anybody know if this was driven by the military to change color?

I would argue that it's a gradual change, and might not have been an intentional change but rather what supplies they were using.

My 1995 era issued M4A1 was very grey in comparison to the black of the 2000 dated M4A1s we received later.

Thanks for the reply. I know my Colt Delta (DH6600) is gray and I picked up a M16a2 upper from a class III dealer that is black but not like the present day black and it has the M4 cuts. Unlike my FN M16a2 I do not see a barrel date on this colt upper, so was trying to date it.

I didn't start seeing blackish Colts until after 2000. Prior to that they were always some sort of shades of gray. Colt from the 80s was a lighter shade of gray compared to Colts from the 90s. I have a few preban Colt lowers and trying to match them to an upper was a pain in the ass. In the end I gave up on Colts and have since moved on.

I've 2 complete Colt uppers: 20" 1/7 A2 with a barrel date of 04/97, & a 16.1" 1/7 M4 bought about the same time.

They are both dark grey.

The A2 matched my pre-ban Colt R6601 Lower, which was made in the early '90's. Since sold the Lower Up north.

As with any chemical bath parts at the beginning of the run will be a different color and texture than ones at the end as the solution weakens. At Colt color cycles of parts are not SN or model specific, when assembling the guns color variation was not a concern as whatever was on hand was used to deliver complete rifles. With Colt (and to a lesser extent GM, H&R, and FN, perceived as smaller production batches) mismatch is authentic, matching receivers were the exception not the norm, (authentically speaking) only someone ignorant of this would want matching AR uppers and lowers. These were military weapons (with Colts adapted for the civilian market) they were not designed, intended, nor marketed to be pretty. If your intention is authenticity, mismatch is more correct, if you want pretty tint the parts the same with sprays like Norrell's, the advantage to this is that with care texture can also be more closely matched. The disadvantage is its no longer original or authentic, altered/restored/modified is a premium that cannot be undone.

These are tools, do you care if all of your screwdriver handles are exactly the same color, really?

"M4" feed ramps were added for the carbines, later in their development, to factor in for the issues related to the shortened gas system and the related impact on the feeding issues of ammunition.  Earlier A2 carbines would see the deeper feedramps with an engraved designation just above the gas tube orifice on the upper received.  M16A4s do not have the M4 feed ramps and still use standard 20" rifle length barrel assemblies with "standard" feed ramps.  As in no M4 cuts.  M4 and M4A1 will have M4 feed ramps.  This is an implementation for military carbine systems.  M16A3?  That should have standard feed ramps.

Remember the only difference between the A2, A3 and A4 is that the A2 has the burst FCG mechanism in the lower with a carry handle upper and an A2 barrel assembly (non- 'F'-FSB), early A3 is just a full auto A2.  A4 has a flat top receiver, no feed ramps and rifle length barrel assembly and 'F'-marked FSB with burst FCG.  Newer A3 would just be a full auto version of the A4 and same barrel assembly.

Civilian A4s and M4s typically all include M4 feed ramps.  My guess would be for business related cost savings.  It's cheaper to stock less components.  This goes for even 20" barrels as well.  You'll find most all 20" AR-15 barrels included with M4 feed ramps.  Even when they come direct from FN consumer sales.  While not military authentic, it's again less inventory for them to manage.

I got a A2 kit from a PD that was upgrading their A2's to M4's and it was gray. They said it was NIB when given to them by the .GOV in the mid 90's and its gray, The paperwork was dated 1991 as manufacture date from what the person I talked with told me when I asked for any paperwork associated with the kit..for collector value..said I cant have the paperwork as it stays with the original lower..and copies were no good as well..

Apples and oranges really.. At least for Colt. Bought many "Pre-black" Colts, and issued others in a 20 year Army career. They more or less matched. 100%? No. But similar shades of grey. I always assumed the color difference was due to the solid film lubricant.

What is your definition of "black?"

There is the charcoal black seen in the late 1980s through mid 1990s.  That seeing said, during that same time frame, '80s grey was stilling popping up here and there.  Also, we were seeing charcoal grey with a purplish tint all the way up into the early 2000s.  

I keep seeing receivers advertised with "early M4 feed ramps," which were not M4 feed ramps at all (same receivers do NOT have an 4 marking above gas tube hole).  If you install a non-M4 barrel on these receivers, you will see that the angles of the ramps match those of a non-M4 receiver.

I have a 96 6551, and it is a much darker gray than my dad's 1994 7.62x39 carbine. But it is a lighter black than a modern one. 

I want to say the last major change to the surface treatment process (that I know of) occurred roughly around the time that the M16A4 was adopted (July 29th, 1997).

The original surface treatment on the M16 & M16A1 was VERY grey in color and was found to be rather susceptible to corrosion in jungle environments like that of Vietnam. Then, @ the early 80s (roughly by the M16A2 adoption date of Nov 20th, 1983), the surface treatment was changed to a darker grey format that was much more corrosion resistant, but still not very scratch resistant. The process was changed again sometime shortly before/@ the time of the A4's adoption. The exact date is rather sketchy as there few a number of A2s (near the end of there contract runs) as well as some early M16A4s that showed up with receivers that ran the complete spectrum from actual purplish-colored to the deep black that we commonly see today. This was a rather hectic time frame for M16-series construction, as FN had just taken over M16-series construction in 1988, and by 1990, the military was involved with Gulf War I. So while the surface treatment process had by then been refined - demand for new rifles (for both the US & our allies), caused many rifles to be sent out with ...shall we say - less than perfect surface finishes, however - by about year 2000 (& pretty much from then onward) true "black" was almost universally, all that would be accepted by military supply chains - at least as concerning newly manufactured rifles received directly from the factory.

Hope this helps you.
FlDiveCop71