Colt SP1 lower spec.s question

[ARMRD]

I've read that the Colt SP1s were made with a larger roll pin diameter for the FCG and were therefore not mil-spec. If so, is this the case with all SP1 models?

My retro gun has an LM upper on a '91-vintage PWA lower. I'm thinking about picking up an SP1, but kind of like the idea of 100% parts 'swapability'.

 

[Teapot]

They are not milspec so interchangeability is lacking.

 

[liberal-hater]

I've read that the Colt SP1s were made with a larger roll pin diameter for the FCG and were therefore not mil-spec. If so, is this the case with all SP1 models?

My retro gun has an LM upper on a '91-vintage PWA lower. I'm thinking about picking up an SP1, but kind of like the idea of 100% parts 'swapability'.

I know a lot about SP-1's, and I'm sure I could answer your question if I knew what you're talking about. What is a "FCG"?

Forward Carrier Group...
Front Colt Goldfish?

All roll pins are the same in the SP-1 as in the M-16. In fact, aside from some machining operations not done on the SP-1 (because of being semi-auto only) and trigger group / bolt carrier replaced with semi-auto only parts, they are the same except for:

Only the front pivot pin is a larger size and captive by this large pin being threaded on the end, and a nut. This was done as an additional step to prevent full auto conversion. Way back then, Colt was the only game in town, and nobody made an adapter to fit a military upper to the large hole SP-1 lower. The SP-1 uppers lacked the small clearance machining cut which would allow function of an auto sear. Colt's idea back then was that even if someone managed to convert the lower to select fire, the large hole upper still would not allow it to function.

Nowadays, an SP-1 lower can be fitted to a normal, common military upper using one of several styles of adapter pins available.

Yes, all SP-1's have large hole, non-detent retained front pivot pins. *Unless there is an extremely rare, early variant that I have never seen or heard of.*

There. I've likely told you much more than you wanted to know.

 

[ARMRD]

I know a lot about SP-1's, and I'm sure I could answer your question if I knew what you're talking about. What is a "FCG"?

Forward Carrier Group...
Front Colt Goldfish?

All roll pins are the same in the SP-1 as in the M-16. In fact, aside from some machining operations not done on the SP-1 (because of being semi-auto only) and trigger group / bolt carrier replaced with semi-auto only parts, they are the same except for:

Only the front pivot pin is a larger size and captive by this large pin being threaded on the end, and a nut. This was done as an additional step to prevent full auto conversion. Way back then, Colt was the only game in town, and nobody made an adapter to fit a military upper to the large hole SP-1 lower. The SP-1 uppers lacked the small clearance machining cut which would allow function of an auto sear. Colt's idea back then was that even if someone managed to convert the lower to select fire, the large hole upper still would not allow it to function.

Nowadays, an SP-1 lower can be fitted to a normal, common military upper using one of several styles of adapter pins available.

Yes, all SP-1's have large hole, non-detent retained front pivot pins. *Unless there is an extremely rare, early variant that I have never seen or heard of.*

There. I've likely told you much more than you wanted to know.

The FCG is was talking about was the Fire Control Group (hammer/trigger, etc.) , but I like your def.s better ;-). Thanks for the info; actually, you told me exactly what I wanted to know.