Quick comparison of the Mil-spec vs Commercial receiver extentions (buffer tube) for AR-15 pattern rifles. This is not a exhaustive study, but a fast way to visually identify possible part spec.
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Milspec will always be thiner tube
If you don’t want to take it out to check the thread alignment, just measure the diameter. Commercials tend to be larger in diameter. Usually around 1.16-1.17”, while the mil-spec should be 1.14”
Very good to know. My new ruger ar556 is made milspec as well as ms trigger and other parts. Not bad for a budget AR. Granted I bought the upgraded version in Barrett brown with the rubberized ambi grip. Over all a great buy for 569$. What brought me here was I noticed it also has a mil-spec castle nut when I was installing a D&z sling attachment to add a single point sling. Steaking it in place to keep it up to its mil-spec quality of course
Great info. Thanx. RC
My two cents on this 'debate' – experience gained from selling the parts.
The OD of an AR-15 Mil-Spec buffer tube is 1.14" (28.9mm). Comm Spec is 1.17" (29.71mm). This is measured at where it goes into the stock, not the lower receiver which is identical on both tubes (the threads have to be the same to fit the same gun..).
Mixing a MS tube with CS stock and vice versa is not recommended. They are different diameters. A MS tube inside a CS stock will be loose and a CS tube inside a MS stock can split the stock.
'Comm Spec' + 'Mil Spec' only applies to the buffer tube and adjustable stocks (which are different diameters).
Other parts such as the castle nut, lower receiver end plate are identical.
So the only part I need to replace is the buffer tube (if I want to change my ar to be able to use a mil spec stock)?
The problem i am having is that i am a larger guy and my "pull" is longer than what the standard Magpul stock will accommodate. This makes it uncomfortable and difficult for me to get the best site alignment on my AR-15. Is there some kind of Longer Buffer Tube or buffer tube extension that i can put on my carbine to make the best and most comfortable use of my optics???
For some reason the buffer tube I bought won't fit into the polymer lower I purchased. The buffer tube seems too thick, and if I force it it'll just strip the thread on the Polymer receiver. If anyone has advice on this please help. Thanks
All this time I thought mil spec and commercial tubes were both the same length, silly me…..lol.
thank you.
Would the retaining plate on a commercial buffer tube fit a mill spec buffer tube or are there two separate types of retaining plates. Thanks
5052, 6061 or 7075. the aluminum codes you threw out there doesnt exist.
this is not what I was looking for but thank you for the education
Is it just the camera angle making the lengths looks completely different?
Having issue with my build lower. BCG won't retract into the buffer tube. Any Ideas. I cut into the tube a few thousands so the detent pin would allow the tube the tube to be flush with the receiver body. Thanks. Phil
I got a mil-spec buffer tube on my lower and the castle nut is tightened down tight, yet I can with one hand turn my stock and loosen it. Any ideas on how to stop this? Never had this issue before and a little hesitant to throw rounds down range until I get a fix for this.
Not sure if anyone has addressed this issue but… If you buy a mil spec buffer tube and don't have all mil spec parts in the rest of your upper you may run into issues with failure to feed a new round. I found this out the hard way, had a mil spec buffer tube that wasn't allowing the buffering spring to go far enough back and the BCG would half chamber a round. Another way to see the difference is; Commercial = six notches on the bottom, mil spec = five notches. Mil Spec is an overall shorter tube as well. I am not a gun guru but I was having major issues until I switched from Mil Spec to Commercial buffer tube, which allowed the buffer spring to cycle all the way back.
What you seeing with the "taller" thread is not a extra milling step to turn down the tube. What that is called is a "ROLLED THREAD" not a cut thread. It's forging the thread with dies, not cutting. Usually done for strength and consistent surface finish for precision torquing, but I'd bet it's done on buffer tubes to allow a thinner wall tube that allows a strong thread area . And it costs WAY more to do, it's not a standard CNCable step.
I have a commercial buffer tube that is flat at the end. Finding out the hard way after buying a milspec magpul ctr. If I wanted to I could buy a milspec buffer tube and it would fit on my ar?
Good video. Accurate info
Joey the tube is thicker, but the threads on a mil spec are raised and at that end of the tube are the same size. I have owned both and interchanged both on the same ar receiver.
Your info on not interchangeable is inaccurate. Please have facts before giving advice. Have a good day.
It's hight btw, highth is not a word…
Does an hk 416 have a mil spec buffer tube?
Another reason they aren't as strong is due to the threads being "cut" on the commercial tube, causing stress and weak points in the material grains, like scoring a piece of drywall and adding to the possibility of cracking. A rolled thread is much stronger and more accurate. Micrometer threads are rolled for this reason. Forgings are the strongest, but more expensive.
Use LMT Thread Roll Products.