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Colt SP1 Lower with a M16 Upper & Bolt Assembly


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#1 OFFLINE   snoopy2u

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Posted Mar. 11 2013 - 07:04 PM

I'm at it again. I need to pick someone's ear and knowledge again.

 

On a Colt SP1, mid 1970's vintage, I have read that putting a M16 Upper receiver on the lower is supose to work. And, I have read on one of the other forums about the need for an M16 upper placed on a lower to have a cammed forward pin for alignment. of course, the M16 upper looks cool, and has a forward assist, and I suspect that the bolt would be designed for a full auto M16, so - 

 

Given that my SP1 would have a semi-auto FCG, can I place a M16 upper onto the lower and still be legal? Will it work properly?

 

What is the purpose of a cammed forward receive pin when talking about M16's or placing a M16 upper on a Semi-auto receiver?

 

Does anyone make a semi-auto bolt carrier for the AR15, having a forward assist?

 

Anyone with thoughts on these points - please offer your feedback. I neither wish to be illegal, make something that will break on me, or cause harm to my components.

 

Thanks in Advance




#2 ONLINE   Nwatson99

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Posted Mar. 11 2013 - 07:21 PM

I am sorry does your lower have the screw for the front take down pin?

 

Bolt Carrier group you want the M16 Full Auto BCG it is more dependable and perfectly legal to have and in place in the rifle.

 

Edit to add; If you have the screw for your front take down pin, then you want this screw so you can install a regular upper to your large hole lower.

DPMS Large Colt to Regular Size Upper Pin


Edited by Nwatson99, Mar. 11 2013 - 07:27 PM.



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#3 OFFLINE   wastedpotentiel

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Posted Mar. 12 2013 - 02:45 AM

..


Edited by wastedpotentiel, Mar. 12 2013 - 03:00 AM.



#4 OFFLINE   snoopy2u

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Posted Mar. 12 2013 - 07:42 AM

NWatson99 - Thanks for your reply. I am not sure that I follow you correctly. I suspect, that on an SP1 lower receiver, I should only need a standard  sized front take down receiver pin to attach a regular Sp1 upper, to a regular SP1 lower?

 

That, If I decide to attach an M16 upper to a SP1 lower, that there is something about either an M16 upper requiring a larger forward take down pin, meaning that an M16 upper, by manufacture has an enlarged forward take down pin hole, as compared to an AR15 upper, and that to mate an M16 upper to a AR15 lower, would require that the forward takedown pin hole in an AR15 lower, be enlarged to accommodate the larger pin hole manufactured in an M16 upper.

 

In that I should keep this screw pin, should I decide to place a AR15 upper onto an AR15 lower, after having attached an M16 upper to an AR15 lower, implies that an AR15's lower forward take down pin hole has to be enlarged to accommodate the lower forward hole in an M16 upper, so that in changing out back to an AR15 upper to a AR15 lower leaves the need to utilize this larger screw pin. I'm trying to understand? Is this correct?

 

And, then, what is the larger screw pin's cam used for, that I read on some of these forums. A regular over sized screw, or over sized pin to mate up an M16 upper to an AR15 lower, would simply be a straight pin or screw. So, what is meant by the cam that I am reading about?

 

Your reply also says that, from your knowledge, having an M16 upper, along with an M16 bolt carrier assembly on an AR15lower, is legal and would not cause any harm, damage or malfunctions in the AR15 lower. That, an M16 upper must be built stronger, or that the bolt carrier assembly must be stronger/better, making this mating more reliable?

 

Do you know if they make an AR15 upper with a forward assist?

Your patience is greatly appreciated.




#5 ONLINE   Nwatson99

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Posted Mar. 12 2013 - 09:49 AM

 

NWatson99 - Thanks for your reply. I am not sure that I follow you correctly. I suspect, that on an SP1 lower receiver, I should only need a standard  sized front take down receiver pin to attach a regular Sp1 upper, to a regular SP1 lower?

 

Not necessarily, the SP1 had both size pins, the .250" and .318", there were very few .250" front take down pins that made it into the civilian market for purchasing, Colt was selling the .250" to Mil and Leo only.


 

 

That, If I decide to attach an M16 upper to a SP1 lower, that there is something about either an M16 upper requiring a larger forward take down pin, meaning that an M16 upper, by manufacture has an enlarged forward take down pin hole, as compared to an AR15 upper, and that to mate an M16 upper to a AR15 lower, would require that the forward takedown pin hole in an AR15 lower, be enlarged to accommodate the larger pin hole manufactured in an M16 upper.

 

No the M16 upper takes the .250" take down pins, so if your SP1 lower has the large hole front take down pin .315" you will need the pin in the link I supplied above to mate the upper and lower together. I know this sounds crazy, but Colt did this and to me it is an abomination and they did this to only allow their large hole uppers to work with this bastiage size lowers.

 


 

In that I should keep this screw pin, should I decide to place a AR15 upper onto an AR15 lower, after having attached an M16 upper to an AR15 lower, implies that an AR15's lower forward take down pin hole has to be enlarged to accommodate the lower forward hole in an M16 upper, so that in changing out back to an AR15 upper to a AR15 lower leaves the need to utilize this larger screw pin. I'm trying to understand? Is this correct?

 

Do not drill out that upper front take down pin hole to match your lower, you will destroy that upper, purchase the reducer pin to allow them to be combined.

 

 


And, then, what is the larger screw pin's cam used for, that I read on some of these forums. A regular over sized screw, or over sized pin to mate up an M16 upper to an AR15 lower, would simply be a straight pin or screw. So, what is meant by the cam that I am reading about?

 

The normal AR15 lower and upper are interchangeable between manifacturers excpet for Colt making this again abomination, Colt had their head up the govt. arse when they did this.

 


 

Your reply also says that, from your knowledge, having an M16 upper, along with an M16 bolt carrier assembly on an AR15lower, is legal and would not cause any harm, damage or malfunctions in the AR15 lower. That, an M16 upper must be built stronger, or that the bolt carrier assembly must be stronger/better, making this mating more reliable?

 

The Uppers are the same, the M16 BCG yes is stronger and heavier thus slowing down the cyclic rate which is more reliable for feeding.

 


 

Do you know if they make an AR15 upper with a forward assist?

Your patience is greatly appreciated.

Yes all Mil Spec Uppers are built with the Forward Assist, Brass, Deflector, and Dust cover.

Now you can buy economy uppers that are absent the Forward Assist, Brass, Deflector, and Dust cover this is a just what it is a economy upper to reduce manufacturing costs which is passed to the customer, but the majority and standard Mil Spec upper unless you specifically order a upper without the listed features comes with everything.




#6 OFFLINE   snoopy2u

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Posted Mar. 12 2013 - 02:11 PM

Nwatson99 - thank you again. This reducer pin. That screw, with an offset cam, that I've seen and heard about - to mate an M16 upper to a SP1 lower is shown on Brownell's site. In appearance this AR15/M16 receiver adapter looks like over sized screw heads on the outer ends, a reduced inner shank, and the inner shank is offset. From this and reading your replies, it must mean that the forward upper receiver holes on the M16 upper are larger than the forward receiver holes on the SP1. I have seen the set up on the net.

 

But - what is the offset cam used for on this adapter? Any idea.

 

Again, my thanks for the world of information and time you have afforded to me.




#7 ONLINE   Nwatson99

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Posted Mar. 12 2013 - 06:37 PM

Can you get us a pic of the SP1 you are talking about, I just want to double check with my eyes which size pin you have.

 

The center spacer is there encase you change out the uppers and go back to the large hole upper as well.

The spacer will come off when using a M16 upper.




#8 OFFLINE   snoopy2u

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Posted Mar. 13 2013 - 02:25 PM

Nwatson99 - I have no photos to send. Everything has been a learning curve for me from reading, talking and trying to understand what I read, and talk about. However, I do wish to thank you for your input, you gave me more insight than I expected. Allow me to go shopping, and if I can't figure it out, or run into a problem - i'll try to connect with your site again.

 

Thank you so much for your input and knowledge.

 

Appreciatively,







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