M4 Type Upper On Colt Sporter Lower

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[ARCHIVED THREAD] - M4 Type Upper On Colt Sporter Lower

Posted: 4/20/2016 2:35:49 AM EDT

I did a search and was hoping for some new ideas or information on accomplishing this.
It seems like the only problem is the front, pivot pin, the rear take down pin seems to be the same.

So from just a few minutes of messing around with a standard AR Upper and my Sporter Lower, it seems like if the pivot lug on the upper is opened up a bit, any AR Upper can be made to fit.

Anybody try this? Is this a bad idea?
Thanks for any help or suggestions.

Posted: 4/20/2016 3:52:05 AM EDT

[#1]

Don't open up the pivot pin hole.
There is a small offset with the Original big hole upper.
Use the adapter that is sold specialy for the set up you're thinking of.
If I'm not mistaken it is sold by Brownells and DPMS.
It's a variation on the original two screw SP1 pivot pin and will cost only a couple of bucks.
I had a .22 upper on my SP1 for a few years and I'm glad I used this adapter.
The .22 upper now sits on a new lower and the SP1 is back in it's original glory.

Stef.

Posted: 4/20/2016 8:02:58 AM EDT

[#2]

What he said ^^^ Get the correct adaptor and it will fit and function perfectly.

Posted: 4/20/2016 8:49:23 AM EDT

[#3]

buy a couple, they tend to break

Posted: 4/20/2016 11:02:47 AM EDT

[#4]

As others have said, buy this :

http://www.fulton-armory.com/frontoffsetpinfcoltlarge-holelowerandsmall-holeupper.aspx

I had a little problem with it binding, so I hit the center portion with a Dremel (just a little bit) and it works just fine.

Posted: 4/20/2016 5:01:20 PM EDT

[#5]

Thanks!!!!!
I forget what my search was when it picked up that Fulton Armory pin. It sure seems like just the thing needed to put a standard Upper on the Sporter lower.

I will report back about how it turns out.

I would like to believe that I would have noticed something off before removing any metal from an Upper, but I sure am glad for the help before even going there.

Posted: 4/20/2016 9:08:46 PM EDT

[#6]

Btw... I also say buy a few... who knows what the future holds for AR's.

And FWIW.... my late 80's Large Pin has used the same offset pin that I bought 15+ years ago.... so mine has lasted quite well.

[ARCHIVED THREAD] - M4 Type Upper On Colt Sporter Lower

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