Colt SP1 compatibilty question

[SnakeEye]

im guessing that the answer will be no, but I figure it worth asking.
would a Colt SP1 lower reciever be compatible with a modern upper reciever?
Everything that ive been able to find indicates that the 1-12 twist rate of the stock uppers barrel is incompatible with modern higher grain ammunition and does not provide sufficient bullet stabilization. Short of using surplus 55 grain ammo, i would like to ideally just slap a modern upper on it. Would this be an issue with pin size/location/allignment?

Thank you

 

[Mike-Mike]

BS I got a old Colt SP1 lower and I put all different uppers on it. You may need to by a different pin because the newer uppers have a small hole and the SP1 has a large hole.

 

[Mike-Mike]

http://blackrifleworks.com/colt-ar15-universal-front-conversion-pin-p-164.html

 

[Wildweasel]

As for the 1-12 rifling yes the 62 grain and up will not be as accurate but there are Plenty of commercial 55 grain stuff available. If you want to upgrade to another 1/7 or 1/8 barrel then go ahead.

You will just need to purchase an adapter for the takedown pins as stated above. (if you want to add a new upper. you can just swap a new barrel onto the original upper.)

 

[stinx]

I put an older SP1 carbine upper on My Colt SporterII lower. I had to swicth hammers as the one in the sporterII was longer and was catching the firing pin.

 

[Chris]

You might also need to use the Colt's Bolt Carrier as the Sear Block can interfere with some of the bolt carriers.

Honestly, either get the Colt rebarreled, or just get a whole new gun as the adapter pins are a royal PIA to use.

 

[SnakeEye]

You might also need to use the Colt's Bolt Carrier as the Sear Block can interfere with some of the bolt carriers.

Honestly, either get the Colt rebarreled, or just get a whole new gun as the adapter pins are a royal PIA to use.

hmm, a couple for and now someone against....this puts me in a quandry. I really wanted to keep the upper in it's original condition and just safe it.
Could you elaborate as to in what way the pins are an inconvenience?

 

[Soxfan9]

I was hesitant to go with a takedown pin adapter. I did, and have had no issues. I have a lot of rounds through this setup, no problems. If you find that you dont like it, it is easy to go back.

 

[Chris]

The conversion is a screw together. You'll need to keep two screwdrivers in your range bag. Also, when you open the action (say to run a bore snake in the middle of a long day of shooting) the pin can turn and require some futzing to realign the receivers.

They do work. It's just a crutch, not a great solution.

Also, you'll find that the finish of the Colt vs. just about anything else will be different. Not an issue if you don't care, but it does look a bit odd.

Functionally, no big deal. Aesthetics and ease of cleaning/take-down are really the only issues. Up to you if it is or isn't a real issue.

 

[SnakeEye]

thank you, ease of takedown is a serious consideration. i want a fully functional, and easily field serviceable firearm. this sounds like something im not willing to tolerate. Ill just keep her together and stock and focus on building up another rifle on another more recent preban colt lower.

 

[Joe R.]

Daniel Defense makes a big hole A4 flattop upper http://www.danieldefense.com/?page=shop/detail&product_id=19 that will work with your SP1 lower with the big pins. Put whatever you want on it for a barrel.

Joe R.