Need help understanding difference in AR15 buffer tubes

[Remington]

I want to put an Collapsible Buttstock on one of my ARs but i have a problem with the buffer tubes.I understand that it is a difference between mill spec and Commercial buffer tubes but i cant seem to figure out if the difference only apply to the buttstock i can mount to it, or if my rifle can use only one or the other.So is there a difference in the part that fastens to the rifle? If so,does anyone know what kind of buffertube is used on rifles from Olympic Arms and Bushmaster? Sorry about my poor english, not my native language

 

[Bartholomew Roberts]

Olympic and Bushmaster use commercial buffer tubes.

You can put any buttstock you like on that tube; but you need to make sure it is built for the commercial buffer tube.

 

[rcmodel]

The difference is:

A mil-spec tube is a milled forging with a stop shoulder at the front end that prevents it being screwed into the lower too far.
The threads stick up higher then the main body of the tube.
The tube measures 1.150" where the stock slides.

Commercial tubes are lathe turned & milled from aluminum tubing, and do not have the front stop.
The threads are the same size as the outside of the tube.
It measures 1.170".
They can be screwed into the lower too far and will prevent the upper from being opened.

The main thing is:
A commercial stock will rattle on a mil-spec tube.
A mil-spec stock will not fit on a commercial tube.

But both have the same thread size and either will fit any lower receiver.

rc

 

[gvnwst]

Luckly, most manufacturers i ahve seen list whether their stock is for a mil spec tube or a commerical, like magpul:
http://www.magpul.com/catalog/index.php?main_page=index&cPath=70_73_110

 

[HorseSoldier]

Magpul also has a PDF on their website that you can print out that has the silhouette cross section of a mil-spec and commercial buffer tube -- just pop off your existing stock, and set your tube on the print out. Whichever one it fits on is what you've got.

 

[Remington]

Thank you