6061 aluminum question

So this question is mainly aimed at Mike at NDS, but chime in if you know. IIRC< there was a discussion here long time back about bronze finishes, and the upside was, it was impurities in the solution or the receiver. What I am wondering is simple - if you had say, a 6061 upper - like an early 603, and were going to have Victor do a bronze finish, but wanted it to match the lower, would it be best to use an earlier NDS 6061 lower or would it matter? I have a 'Blaine' lower but hate to use it since it's already set up for my XM16E1, but if the finish will look different, maybe it's worth it. Ideas?

7075 comes out of the hardcoat as a tan/bronze color, and then has to be dyed gray or black.

6061 comes out of the hardcoat a dark, charcoal gray (depending on run time)

The best bet is to email Victor and find out exactly what he wants to work with.

Interesting topic and response from Mike. Any ideas when retro Colt aluminum switched from 6061 to 7075? I assume the first batches of the Model 01 were 6061. But I have two 601 uppers with their original anodizing. One has that dark gray, but is showing bronze around the wear points,, especially around where gun oil sits. The other is just flat out gray that is light and thin. I can still see the tell-tale original anodizing "streaks" in the anodizing. You can really tell by looking at the lugs on the upper.

This is a interesting topic I wish there was more I could say about it. I have a couple 601 charging handles with the bronze / Gold undercoat and a couple without. Being very early parts I would think they would be consistent. Near as I can tell most of the gold undercoat is on parts made before 67. Mainly have seen it on Mags, charging handles and upper and lowers. I am assuming the changeover from 6061 to 7075 is when the gold / bronze undercoat dissappeared...? Other aluminum parts from the era lack the undercoat...like slip rings, mag buttons, trigg guards, etc.

Victor will have to answer the color match question. When he did my light greenish yellow receiver set, IIRC he said it could only be done with both receivers being 6061. It will depend on the color. Now I'm in the same boat Morg.....I want to match a 6061 NDS 601 lower to an early bronze upper.

Megaro

Could you elaborate on what chemical process you used to get this beautiful worn finish ? I would really like to try this.



NDS list of alloy types


NDS AR LOWER RECEIVER IDENTIFICATION GUIDE

NDS-16A1:

BLAINE MARKED, “HIGH TEXT”, A2 FORGING, 7075 ALUMINUM
SN: A00001-A00204

BLAINE MARKED, “LOW TEXT”, A1 FORGING, 6061 ALUMINUM
SN: A00205-A00403

EDINA MARKED, “LOW TEXT”, A1 FORGING, 7075 ALUMINUM
SN: A00404-A00605 AND FORWARD


NDS-XM16E1:

BLAINE MARKED, “HIGH TEXT”, A2 FORGING, 7075 ALUMINUM
SN: B00001-B00105

BLAINE MARKED, “LOW TEXT”, A1 FORGING, 6061
SN: B00106-B00274

EDINA MARKED, “LOW TEXT”, XM FORGING, 7075 ALUMINUM
SN: B00275- AND FORWARD


NDS-601:

BLAINE MARKED, “HIGH TEXT”, A2 FORGING, 7075 ALUMINUM
SN: C00001-COOO55

BLAINE MARKED, "LOW TEXT", A1 FORGING, 6061 ALUMINUM *EDITED*
SN: C00056-COOO82

EDINA MARKED, “LOW TEXT”, A1 FORGING, 6061 ALUMINUM
SN: COOO83-C00157

EDINA MARKED, “LOW TEXT”, 601 FORGING, 7075 ALUMINUM
SN: C00158- AND FORWARD


NDS-16A2:

BLAINE MARKED, “HIGH TEXT”, A2 FORGING, 7075 ALUMINUM
SN: D00001-D00160

Megaro - that really is outstanding. Why did I never see that pic? I notice it's a later lower also. That's kind of what I'm striving for with the XM177E1 receivers - like to do a 'Goldy' build. Interesting that Mike said that 7075 comes out of the hard coat Bronze, not the other way around. Huh? Wonder if we could Victor to comment.

ETA: FWIW I just emailed Victor to see if we can get some clarification on what he recommends. What's hilarious to me is all the time we spend trying to make the receiver colors match when probabaly 85% never did - Uncle Sam could care less. There's a transferable carbine on Autoweapons.com that is a good example of this. Maybe why they changed to black anodizing? Anyway, it's mine, and I'm pickier about things like that than the .gov

I'm just going by what Victor told me.

I believe the 6061 goes through various shades before it goes completely dark, kind of like a part when you heat treat it.

Megaro

Could you elaborate on what chemical process you used to get this beautiful worn finish ? Others would really like to try this.

Megaro, that finish looks awesome !

IIRC, all that I used were soft rags and Mother's Mag polish. Took a long time to do it this way. I think that was the one that I intentionally did not use any kind of abrasives to weather the finish. Also, I had to go through a few sets of NDS uppers and lowers to get an even color match. Mike's explanation makes sense to me because I think all I did was gently remove the top gray and just got the bronze-y color underneath I have also found through weathering other NDS / US Anodizing parts that there is a very fine line between that cool kind of bronze color and just the raw aluminum. I think I also when I got close to the point would kind of water down my rags so it wouldn't have as much Mothers on it. Hope that helps. It's a time consuming process to do it that way, but it sure looks cool !

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