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View Full Version : Receiver Extension tubes: Mil spec vs. Commercial


akjunkie
10-20-2009, 12:44 AM
Wow, alot of good information.

On a side note does anybody know if Rock River sells Mil Spec or Commercial?

Majority of my Stock sets are from them. I am in the process of buying spare parts for my rifles and the Extension tube is one item i like to stock up on.

Thanks for all the replies.

akjunkie
10-20-2009, 12:45 AM
Wow, alot of good information.

On a side note does anybody know if Rock River sells Mil Spec or Commercial?

Majority of my Stock sets are from them. I am in the process of buying spare parts for my rifles and the Extension tube is one item i like to stock up on.

Thanks for all the replies.

akjunkie
10-20-2009, 11:51 AM
I've been seeing alot of ads for Mil spec vs. Commerical extension tubes.

Can someone explain to me the difference between the two?

Will a Commercial stock fit a Mil Spec tube and vice versa?

And if there is a difference in Material used? Steel vs Aluminum, etc.

Why do MFGs even bother making Commercial Spec stock assemblies?

hoffman259
10-20-2009, 11:53 AM
Try the search function. Been covered a lot

Someoneelseok
10-20-2009, 11:54 AM
http://www.magpul.com/pdfs/technotes/ctr/buffertubeid.pdf

diameter of the tube to accept the stock. not sure, but...do commercial stocks have 6 positions, instead of 4 on milspec ones?

Also, Milspec size seems to have more of a selection of stocks.

technique
10-20-2009, 11:57 AM
Commercial is a bit larger in diameter IIRC. So a commercial will go on a Mil-spec tube but will have a lot of play...so its not really a viable option.

Commercial tends to be a wobbly even on a commercial tube (YMMV).
Mil-spec is generally more of a tight fit with less wobble.

I stick with the mil-spec. So I have limited knowledge on the commercial.

mds2004
10-20-2009, 12:12 PM
Either tube will fit on your receiver. Commercial dimensions are slightly larger. You can put a commercial stock on a Milspec tube but there will be much more play. I've had better luck on tighter tolerances sticking with Milspec. Supposedly Mil-spec is stronger too but that I do not know of personally. FWIW Im sure you will be fine with commercial.

CHS
10-20-2009, 12:20 PM
A true mil-spec tube is made from a forging of aluminum, and slightly smaller in outside diameter than a commercial tube.

Commercial tubes are made from anything, and many times not made in the US.

Commercial tubes are not as strong as mil-spec tubes and have a larger variance in manufacturing.

Crappy stocks like UTG and CAA only come available in Commercial. Some of the nicer mil-spec stocks only come available in Mil-spec.

If you have the choice when building, go mil-spec.

ALL tubes, commercial OR mil-spec, are threaded for the standard threads in the rear of a receiver. Commercial vs. Mil-spec doesn't have anything to do with lower compatibility. Just the stocks they can accept.

missiontrails
10-20-2009, 12:28 PM
There is 50% milspec, 100% milspec, and then there is commercial. 50% milspec tubes are 1.1480 in diameter, but are made from softer 6061 aluminum. 100% milspec are same diameter, but made from harder 7000 series aluminum, and the TDP does not specify forged or extruded. The threaded portion of the tubes also have slightly higher threads that fully engage the female threads in your lower. Commercial tubes are 1.1725 (ish), and are made with 6000 series aluminum. Also, the threads are a little lower than milspec threads, and do not fully engage your threaded lower.