Is this what I think it is? [Archive] - Glock Talk


View Full Version : Is this what I think it is?

12-14-2012, 18:14
An acquaintance and I were discussing AR stuff when the topic turned to old type ARs eventually turning to Colt SP1s. Most of you know that the SP1 was a sporter/civilian model. It had A1 sights, slabsided upper (no forward assist or shell deflector).

So he says, "hey, I have an stripped SP1 upper receiver, do you want it?" "What do you mean want?" I ask. "You can have it, no charge. I have no use for it and am never going to build a rifle with it." says he.

So he brings it out, I look it over and see that it has never been used as in, never been made into a rifle. No marks, no scratches, no wear, nothing. It has the rear sight but no dust cover ever installed. That is unusual as I don't think Colt sold stripped uppers.

Long story short I took it home and compared it to my SP1 upper...

But guess what? They are not the same. Can you tell the difference? (not counting the ejection port cover or color)

How bout now?

12-14-2012, 18:27
Pivot pin hole and the inside shape of the carry handle look wrong.

12-14-2012, 20:06
The bottom left corners are different??

12-14-2012, 20:11
Small front pivot pin hole. Where are the forgings?

12-14-2012, 20:22

12-14-2012, 22:00
The civilian Colt SP1 upper has a large front pivot hole because they used an offset two piece screw so they couldn't be put on standard lowers. You can use an offset sizer in the hole for use with non Colt lowers.

The stripped upper has the correct stampings on it to indicate that it is indeed a Colt. The angles and corners on both are identical, the camera angle makes them look different. Hard to say when it is was made but the slab sides (no forward assist) mean it was early and the only slab sided uppers that didn't have large holes were military uppers. That means an early military upper that was never built. If that is true then it is pretty rare. Possibly early Vietnam era M16, maybe even an earlier 601 or 602. The guy who has this claims he found a box of them when he was in the Marine Corps in the 1980s working as an armorer. Since they were using M16A1s and were switching to the A2s he liberated one for future use. I don't know if that is true but it would make a nice lightweight rifle or cool retro build.

12-15-2012, 06:48
Looks a lot like a 601 upper

12-15-2012, 12:55
Upon further review I have determined that it is a Colt 604 upper.

This upper has now been switched with my SP1 upper which is now for sale.