Colt Small Pin Upper?? > AR-15 / M-16 Retro Forum

Posted: 5/24/2007 2:13:43 PM EDT

I'm learning about retros here to bear with me please...

This seller says his Colt upper is a "small pin".....and it will fit anything OTHER than a Colt lower?!?!?

GunBroker Link

How can this be?

Can someone help me out here?

Posted: 5/24/2007 2:26:29 PM EDT

[#1]

He means that it will not fit a Colt SP1 lower or any other lower with a "large pin". Anything with a "small" front pivot pin hole will fit this upper.

Posted: 5/24/2007 5:31:54 PM EDT

[#2]

I've bought 5-6 barreled uppers from him in the past. You have no worries buying from him.

Posted: 5/25/2007 6:04:28 AM EDT

[#3]

Quoted:
He means that it will not fit a Colt SP1 lower or any other lower with a "large pin". Anything with a "small" front pivot pin hole will fit this upper.

So in my effort to do a retro build, should I be looking for a "large pin" upper and lower due to their being more common?

I heard that Colt produced a few with a different size pin so that they were not interchangeable.

Is there a way to look at one in a picture and tell if it is large pin or small pin?

Posted: 5/25/2007 6:23:41 AM EDT

[#4]

Quoted:
Is there a way to look at one in a picture and tell if it is large pin or small pin?

Look towards the bottom here: www.biggerhammer.net/ar15/uppers/

mike

Posted: 5/25/2007 7:12:35 AM EDT

[#5]

Quoted:

Quoted:
Is there a way to look at one in a picture and tell if it is large pin or small pin?

Look towards the bottom here: www.biggerhammer.net/ar15/uppers/

mike

Cool ! Thanks Mr. Wilson..

Here's what I'm reading:

Colt owners often refer to having a small or large hole upper receiver (and corresponding lower receiver). Small hole receivers of .250" are the "milspec", but during early production by Colt for the civilian market, they produced rifles utilizing a .315" spec, so as to preclude use of military uppers on civilian lowers. This production lasted until roughly 1993-1994. As a general rule of thumb all Colt "unblocked" lower receivers, are large hole, while pre-ban "blocked" lower receivers represent transition years where occasional variations popped up.

So.....if I'm trying to do a retro build.....and I find an "M16 upper" on EE or Gunbroker, it would be safe to assume that this is a "small hole"....and therefore would force me to find a small hole lower....which would be hard to find, especially complete, since this would be originally a machine gun and thereby illegal for regular joes like me..

However, if I find an A1 slabside (same as SP1?) then this would automatically be a "large hole" upper, and would avail myself to a wider selection of lowers both complete, and stripped like Nodak Spud carries?

Am I correct in what I am thinking?

I'd like to find a pencil barreled upper with the duck bill flash and do a build...but this sounds like it would be much harded to find in parts than simply piecing together SP1 parts as I find them....?

EDIT: Here's what I want:

Posted: 5/25/2007 10:15:30 AM EDT

[#6]

Quoted:
So.....if I'm trying to do a retro build.....and I find an "M16 upper" on EE or Gunbroker, it would be safe to assume that this is a "small hole"....and therefore would force me to find a small hole lower....which would be hard to find, especially complete, since this would be originally a machine gun and thereby illegal for regular joes like me..

This isn't nearly the chore you are imagining it to be. Every lower receiver ever made is small hole, except for Colt civilian/sporter models predating the mid 90's.

Large hole uppers are a pain. Get the M16 upper, then look for an older A1 style lower by SGW, Palmetto or the like, or get one of the new Tactics or Nodak Spud retro lowers.

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