Mil-spec upper on old SP1 lower?

[RJG]

Howdy,

I’ve heard that it’s possible to put a mil-spec upper on an older Colt SP1 lower - the SP1 has the large diameter screw-type take down pivot pin. Does anyone have a link or know where to get the conversion pin/bushing to do this? Are there any risks or downsides to doing this? This would be for a registered-transferable SP1 auto conversion that I’m thinking of buying.

Thanks -
RJG

[Cuda444]

Bushmaster makes a Colt large hole lower to small hole upper adapter... It's like 6.50 plus shipping. In fact:

http://bushmaster.com/catalog_parts_...s_p2.asp#NES06

[PALADIN-hgwt]

xxxxx

[Stretz Tactical Inc]

I wouldn't use the bushmaster pin. I had one lock tited in place and took trident concepts' advanced combative carbine course for 3 days. Half way through day one I was wondering why my gun kept jamming and looked down and noticed there was no pin in the gun anymore. Someone loaned me a gun for the rest of the day and then sold me a spare bushmaster pin on day two. I lock tited that - (didnt have time to let it set in) That pin continued too come loose and I had too keep tightening it between relays for the remaining 2 days. While we were shooting, I looked over and advised the guy who sold me the pin that his pin was now missing out of his gun. I bought a new colt pin from specialized armament since then - which is a little different. So far so good, but I haven't taken any courses since (so no hard use to check how good it is)

[RJG]

Thanks for the replies. The DD upper looks nice but I want to use my existing mil-spec uppers. Sounds like Colt and BM make a solution that should work as long as the screw doesn't come apart.

Thanks,
RJG

[Robb Jensen]

As already stated to use a mil-spec pivot pin upper that you already have with a large pin lower will require a two piece offset pin.

The big hole Daniel Defense is the best set up for your lower, it comes with a large .315" Push Pin so that you don't have to use tools to get your upper apart from your lower.