View Full Version : Replacing upper receiver on a colt sp1?

02-18-2012, 7:29 PM
My dad wanted to replace the upper on his sp1 so he could get one actually cambered in 5.56 and with forward assist. However, I guess it's not as simple as just switching them out since the front takedown pin is larger than the holes on the uppers being currently manufactured. So basically I am wondering what some options might be. Thanks for the help.

02-18-2012, 10:01 PM
Is your lower a large pin as well or do you have the kit to fit your sp1 on a std lower? I am in your sp1 if you get it worked out... Let me know what your trying to do maybe I can help you.. I have all the tools and parts to help.. PM me.

02-18-2012, 10:14 PM
Im sure there is a manufacture that makes a Pin conversion, I know Ive seen them somewhere....

02-18-2012, 10:49 PM
Brownell's sells the pivot pin conversions. I think about $10 or less.
Common part and easy to do.

02-19-2012, 11:09 AM
Brownell's has the adapter pin here (http://www.brownells.com/.aspx/pid=24948/Product/AR-15-M16-RECEIVER-ADAPTER). I had one break on me but it had a lot of mileage on it. That's what I used until I laid my hands on a Daniel Defense "Big Hole Upper" (https://danieldefense.com/big-hole-upper-receiver-assembly-b.html) which doesn't need an adapter and comes with a detent retained push pin (although one could use the original SP1 double-headed pin if they wished). Look around, you may find them cheaper than Daniel Defense lists them.

02-19-2012, 12:27 PM
Thanks everyone. I was able to find exactly what I was looking for.