Need help ID this upper

Customer brought in a “Colt Defense” M4 Carbine bought earlier this year in another gunshop. The carbine come from Italy (IT 2018 laser-marked on the barrel, Italian proof house stamps on upper, bolt carrier & barrel).

At 25m, the barrel is slightly keyholing. I didn’t give it a check myself, just writing what the customer told me. He tried only one brand of ammo in it (GGG 55gr). My first step will be to try another brand of ammo (and also heavier bullet).

But I think that the only part made by Colt on this “Colt” is the lower receiver itself…The barrel is marked “5.56 NATO 1/8”

If members can help me to identify the other parts, I would be very pleased :slight_smile:

Thank you for your help !

The only thing i can tell is that it has a mueller industries upper

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Sounds like your customer needs to take that franken turd back to the store he bought it from, and get his money back.

aftermarket BCG - definitely not mil-spec
unmarked upper - not a Colt for sure

Does not appear to be a Colt based on the pcis.

Yes, it’s what I told myself: neither the upper, the BCG or the barrel are Colt. The bolt is unmarked.

Looks like an Italian distributor is importing Colt Defence firearms and rebuilding them with their own-sourced upper assembly. The charging handle is very, very soft. The barrel extension is parkerized.

I wonder if they import only lower receivers to assemble with their upper or if they import the whole Colt carbine and sold the upper group apart.
I think they only import the receivers.

“franken turd” haha






But the importer swear those are “all original Colt, made to our own specifications”.

With a unchromed 1:8" barrel 14.5" barrel ?

Yeah…sure.

Definitely not a Colt bcg, fire control group, or barrel. Looks like Chinese junk.

I’m not an expert but I think your customer has been duped.

Mueller Upper:Probably finished by Aero for PSA

BXG… if you look at the stake job on the Key, you can at least gauge the quality…

Frankly I’d bet they took some crappy parts and trying to pass it off.