View Full Version : old colt upper won't fit on my new milspec lower.... how to fix?

09-05-2010, 6:26 PM
i would like to test out a 20" colt upper but the front hole on the upper receiver is larger than the one on my new OLL. Is there someway I can make an adapter so it doesn't move around on the smaller pin size from the OLL? Can I do this in the garage?

09-05-2010, 6:28 PM
You can buy an adapter, like this one http://blackrifleworks.com/colt-ar15-universal-front-conversion-pin-p-164.html

09-05-2010, 6:29 PM
There are pins specifically for that. Check brownells. I believe it is called an offset pin.

09-05-2010, 6:31 PM
Well Colt uppers are made that way to make them mate up w/colt lowers only. You can try sleeveing the hole in the upper to bring it's inner dimension more in line with the lower's pin. .

Edit: Adaptor pin. Dont think this will work for him in that he wants to put a colt upper on a new lower.

09-05-2010, 6:32 PM
You have an SP1 upper. Get the bushing that goes in the front lug of the upper. That way you can use the standard take down pin, instead of the funky offset screw.

09-05-2010, 6:33 PM
anything i can get at home depot or lowes tonight to sleeve it and use at the range tomorrow or am I all out of luck?

09-05-2010, 6:35 PM
also I have a normal milspec lower (noveske) with small pin holes, so the adapters in the links are for the other way round... i have a large hole front pinhole on the upper receiver....

any suggestions?

09-05-2010, 6:41 PM
You need this the bushing not the pin.


09-05-2010, 6:43 PM
The bushing is basicly a sleeve. Dont know if Lowes or HD will have some tubing that will meet both the inner and outer dimensions you need. Best bet is take a caliper to the holes and pins and then compare measurements on what's available at the stores.

09-06-2010, 8:06 AM
You need Brownell's part #231-000-181 AR15/M16 Pivot-Pin Adapter Bushing $3.19

John Browning
09-06-2010, 8:08 AM
You need the proper bushing, not something from the hardware store. If you want to buy your rifle parts at Lowes, get an AK. :)

09-06-2010, 9:28 AM
anything i can get at home depot or lowes tonight to sleeve it and use at the range tomorrow or am I all out of luck?

Yes. I have seen a guy use electrical tape, two bushings, a bolt, two nuts and two washers.

He took the nut and figured the exact position the nut had to be in the upper in order for the bolt to pass through the lowers two pivot holes.

Of course the nut was off center. He used electrical tape to fill the lobsided gap.

He then used bushings to fill the lowers pivot holes since the bolt was a lot smaller then a standrad pin.

the washers make sure the bolt doesnt slip through the holes (one on each end)

and the last nut crushes the upper and lower together making a tight non-wiggle fit.

MS paint pic incomming....:D