I've seen this is and that isn't, but what I haven't seen is how to figure out the difference for yourself.  So...

1.  What is the difference between "mil spec" and non?  i.e. what dimensions are different?  Please give a good description of what to measure and where.

2.  What brands (definitively) are and are not spec?  Industry folks, feel free to chime in.  i.e. I have a doublestar 6 pos. stock tube - spec or not?  

That being said, please keep the "+1" posts to a minimum and I will edit this to read as a list of who's in and who's out (of spec).  Hopefully this will be helpful for anyone looking to replace/upgrade their stock.

ETA:

Mil Spec:

Colt
CMT
LMT
Vltor


Non Mil Spec:

RRA
Bushmaster

try a search for "mil spec" or "m4 stock" ect....there have been several long topics on this recently

basically, most comercial AR brands (ABDR,etc) and manufactures buffer tubes and stocks are NOT mil-spec--i'm pretty sure yours is not

mil-spec tubings are supposidly more resiliant and stronger through better manufacturing methods (forged i belive )the threadings are also more refined

non-milspec tubings have a little more diamter over the mil-spec tubes and they will not fit a mil-spec stock; i have had both, and the mil-spec stock has a little more play, but that is normal

CMT/Stag are the current best, most availble stock/tube mil-spec makers that usually run ~$70-80 (colts are also mil-spec i think); non-mil specs usually run $10-$20 less

LMT and Vltor are also Mil-Spec, small size diameter buffer tubes and buttstocks.


REF: Choosing the Best Collapsible Stock for "You" thread link

RRA and Bushmaster are non-milspec.  Buffer tubes are larger in diameter than the mil-spec ones (LMT, Colt, Vltor, etc...).

Actually has to do with the final maching IIRC..

Someone correct me if I am wrong.. but I understond that the milspec ones where threaded, and machined a bit more to a smaller diamer after threading..

The comercial ones require less machine and are cheaper as such, they are just threaded and finished.

This is why a milspec stock won't fit a comerical receiver extentsion, but a comercial stock will fit a mil spec one(though it will be loose)..

Could be wrong...

Quoted: Actually has to do with the final maching IIRC.. Someone correct me if I am wrong.. but I understond that the milspec ones where threaded, and machined a bit more to a smaller diamer after threading.. The comercial ones require less machine and are cheaper as such, they are just threaded and finished. This is why a milspec stock won't fit a comerical receiver extentsion, but a comercial stock will fit a mil spec one(though it will be loose).. Could be wrong...

sounds right...comercial ones are easier and cheaper to make, but i'm not sure how its threading is machined vs the mil-spec ones

I believe spec tubes have the threads rolled in, while the non-spec are cut, hence the larger diameter.

Rolled is always prefered, since no material is removed in the process.

Pretty much everything being said here has been covered elsewhere.  

Can someone take a mil spec tube and measure it vs. a non mil spec tube?  The actual dimensions are what I'm looking for.  Please list where measured and to as small a figure as possible.

thanks

Quoted: Pretty much everything being said here has been covered elsewhere.   Can someone take a mil spec tube and measure it vs. a non mil spec tube?  The actual dimensions are what I'm looking for.  Please list where measured and to as small a figure as possible. thanks

I'm looking for the same info, I can't find it in any of the threads that came up when I searched.  I have 2 tubes at home, 1 that I know for sure is commercial, the other seems slightly smaller...when I measured there was roughly .020" difference...I don't know how much difference there is supposed to be between the 2 (commercial vs. mil spec).

Mil-Spec buffer tube OD = 1.150"

Aftermarket buffer tube OD = 1.170"


You're correct, the non-Mil-spec buffer tube OD is about 0.020" bigger than the Mil-spec tube.


Ref: What's the Difference Between Mil-Spec and Non Mil-Spec Buffer Tubes? thread link

Quoted: Mil-Spec buffer tube OD = 1.150" Aftermarket buffer tube OD = 1.170" You're correct, the non-Mil-spec buffer tube OD is about 0.020" bigger than the Mil-spec tube. Ref: What's the Difference Between Mil-Spec and Non Mil-Spec Buffer Tubes? thread link

Good deal, thank you much!  I thought those were the measurements I came up with last night, but couldn't remember exactly off the top of my head.

Excellent!  Those were the measurements I was looking for all along.  Is the diameter of the tube the only dimensional difference (other than manufacturing methods)?  Obviously the threads for the receiver extension would have to be the same size and all.

Quoted: Excellent!  Those were the measurements I was looking for all along.  Is the diameter of the tube the only dimensional difference (other than manufacturing methods)?  Obviously the threads for the receiver extension would have to be the same size and all.

You're correct, the threads are the same but also using a non Mil-Spec buffer on a Mil-Spec tube would make the buffer rub in the inside of the tube causing to slow the carrier down to make it short stroke.

Ref: Short Stroke Problem thread link

Also about last year a Vltor rep told us of a horror story about some guys that tried to install a Mil-Spec Vltor Modstock on a non Mil-Spec buffer tube.

The Vltor stock got stuck pretty good on the non Mil-Spec tube, no way to get it out, so the customers sent it back to Vltor's factory which they also admitted their error.

This was actually a nightmare for Vltor because the factory sent new free replacement stocks to some customers.