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Complete Colt M4 marked lower receivers- Heads Up!

12K views 73 replies 19 participants last post by  colrhino 
Hope you can swing it, only wish I could afford a few more! Picked mine up today, a couple of pics as promised. H buffer, 2 position stock.
Congrats of your new Colt lower half.

Something that's not the same as the 6920 lowers are the CR serial number prefix and the two position receiver extension.

Colt had the two position receiver extensions on their civilian and law enforcement carbines between 1985 and around 1998, before Colt Defense was created in 2002.

You could probably replace the buffer tube to your preference if you want to or just keep it as is.

What are the hammer and trigger pins sizes, small mil-spec 0.154" or the oversized 0.170"?

If you don't have any measuring instrument, just put your firing pin in the hole, if it wobbles it's large hole, if snug then it's small hole size.
 
Well, I have to figure out how to fix the adjustable stock lever. It's just flopping around on the screw. Any advice?
View attachment 461145
Just slide the buttstock slightly forward or backwards so the screw will move upwards and seat on the position holes of the buffer tube.

It looks like the pin/ screw is in between position holes of the buffer tube, there should be four positions, closed all the way forward (shortest stock length), two middle positions and the fourth is all the way towards the rear (longest stock length).

Colt finish quality are not good, they're mass produced so rifles are just stacked together, see my attached pictures of the Colt factory below.

Myself I've been a Colt AR owner for a long 47 years and had more than a dozen rifles and carbines all that time, I never had a perfect finish, but I had seen others are a little worst than mine.

My suggestion is get a touch-up finish flat black pen for aluminum and apply it on the imperfection, then just use CLP lube or oil and apply, then remove/ wipe the excess lube.

The anodizing process is actually very deep in the aluminum material so if scratched there are still finish impregnated on the material and it will protect it from any corrosion.
 

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