I have a Colt AR, A2 configuration. I want to replace the solid stock with a telescoping carbine type. The A2 length of pull is too long for my daughter to manage comfortably.

I've read several threads on arfcom on the topic and I'm still confoosed. Do I need a commercial or Mil spec buffer tube and stock to fit my lower properly? Or does it matter? The rifle is a Colt sporter that I bought new back about 1990 or so. Markings below.

Either will fit on the lower, Just make sure you get a stock that matches the buffer tube. 

Attached File

The lower doesn't matter. Order a milspec tube and milspec stock as they're most popular.

Mil spec tube will give you more options for stocks.
Make sure you get a carbine spring, too.
ETA: and buffer.
ETA:

Wow! I sneak off to pick my teenager up from work, and return to a hefty dose of wisdom. Thanks, folks.

STNGR USA makes a very nice mil-spec buffer tube for very little money ($17) with free shipping.

7075 Aluminum, nice anodizing and did I mention free shipping?

https://www.stngrusa.com/collections/buffer-tube

Says Colt Competition.
I thought that these guys were just a company licensed to use the Colt name

OP you should buy a milspec tube just because there are more stock options and they are often cheaper. You will also need an end plate, castle nut, carbine buffer and spring as well.

As others have said go mil-spec, and ensure the tube is 7075 aluminum. Some venders use
the term “mil-spec” to mean the diameter of the tube, but the tube is make with 6061 aluminum.
If the stock set description does not mention 7075, then most likely it is 6061.

I am partial to this old school stock set, but M&A has high shipping
CAR Stock set

You can keep it simple and cheap with something like this............
Mil Spec 6 position Stock Hardware Kit-AR15-USA Made

Or what I usually do is something like this........
BCM AR-15 Milspec Carbine Stock Hardware MOUNTING KIT (Milspec)- Standard Carbine Buffer 2.9oz.

That way you get everything in 1 simple package. All you need is to pick your flavor of butt stock that is Mil Spec sized for the buffer tube.

Just the fact that they have been either unsold and unnoticed now for months is remarkable to me, either that or they must have thousands for sale.

I bought a handful and they're EXACTLY the same as every single Hartford-made Factory Colt Defense 4-position RE I've ever seen installed on a Factory Colt Defense LE6920/6720-lower, down to the forged/impact-extrusion "blemishes" on the exterior and the incredibly-smooth and well-polished interiors (they come with the dry-film moly-lube applied inside).  Good deal for $15.00 per (#AR64073).  

They also have the Factory Colt Defense USGI "gold" extractor-springs with black-inserts for a buck (#AR64026).  Factory Colt Defense Carbine "copper" recoil/action-springs for $1.99 per as well (#AR62373).  Buy a handful of both, you won't be disappointed.

It appears Colt Competition went to the effort to use really important Factory Colt Defense (Hartford, CT sourced-parts) where it would do them the most good, at least with regards to long-term reliability and durability.  Good luck.

https://www.righttobear.com/Mission-First-Stock-Buffer-Kit-Black-p/bmsmil-bl-msbk-blk.htm
These are good stocks and a great price.

I've gotta remember to check back more often when I ask a question on here. Folks, thank you all again for taking the time to educate a noob. I appreciate it.

So... I sorted out the stock issue kind of by accident. Went to the Manchester VT gun show, and won a gift certificate as a door prize. Had to use it before I left, so I swapped it and five bucks for a stock that should do the job. Figured how far wrong could I go for $5? Should have it together this afternoon, and we'll go from there.

Got it together:

https://thumbs.imgbox.com/6d/d3/tBdGJ3V4_t.jpg

Took it and the daughter out to the range yesterday. She loves it! The rifle fits her now.

Awesome