AR15 buffer tube sizes

[Buckshot Wade]

A question for all you AR-15 whizz-kidz. When in the world did they come up with the idea of having two different diameter buffer tubes? That's insane! With the recent purchase of a Bushmaster Carbon 15 model, the buffer tube on it is larger then my Anderson Manufacturing AR-15. Sadly, I didn't find this out until after I had ordered a replacement stock for the Bushmaster. Mil-spec is 1.148" and commercial is 1.17".
So can anyone explain why there are two different diameter buffer tubes on a single style weapon? To my mind that is just stupid! Mil-spec is fine why add the commercial size? I hope one of you Lads can answer my question because this is driving me nuts. And sadly the butt stock that I ordered which is a cute little devil, is not going to fit my Bushmaster. That is not what I wanted. So you can tell I'm a little frustrated.

 

[grasshopperglock]

The AR15 was never a military weapon until the government made it that way. M4 specs include a different size recoil tube.

The civilian size tube came first. A throw back to the original design.

 

[Sam7sf]

Here’s the answer in short: your receiver will accept both. With having a larger o.d the commercial extension tube takes different stocks. It also typically has a slant on the butt of the tube. Also there is no spec requirement for commercial so that’s why many are made from 6061. I prefer mil spec 7075 extruded tubes. But if we think about it, both will have very similar strength. The 6061 tubes are simply cheaper to produce.

I personally like mil spec because stocks are more common. Not to say commercial isn’t. Now a days a lot of businesses have em’ in stock. You see them a lot on cheap builds such as ruger, bushmaster, and who I worked for. Along with cheaper delta rings that don’t fit furniture right. Commercial is cheaper. So...most are Chinese. Shocker. They are very cheap.

 

[Buckshot Wade]

Yeah, gotcha now. Thanks!
Its been 40 plus years since I worked on this style weapon. Its changed some from the stock standard M16 huh? I remember the CAR15 with that collapsible stock and shorter barrel back in the day. In my AO only E-6's and above could be issued one if available.

When the buttstock arrives I'll likely mount it on my Anderson model with the mil-spec system.
Like I said in my intro joining up here, I'm interested in learning about new stuff. Sure, I was a hell-of-a gunsmith, but that was a long time ago. Loads of new stuff now that I'm not even remotely familiar with.

Thanks guys. I got this now.

 

[Sam7sf]

Oh I almost forgot. Your end plate. Order from a good source like stag or bravo. Many end plates use what I call Chinese diarrhea steel. When you go to stake, the material will sometimes give or sheer off if you work an angle. I know some people will just punch straight down but I prefer no gap between the material and the slot in the castle but. Plus this way it gives you an easy dremal point if you need to change tubes. Anyway, stag plates are really good. They are just right. Soft yet strong and can take a pounding. You’re welcome there’s your out of context quote.

 

[Southpaw]

You’re welcome there’s your out of context quote.

It's no fun that way.

 

[Buckshot Wade]

The tube on the Bushmaster is, as we figured out is a commercial unit, but it has only two adjustments too. Fully extended of fully collapsed. Shoulda figured huh?
But that's ok. Found a Mil-Spec replacement for a reasonable price. I'll order one soon and fix things up right.
Fellas, again, thanks for the info.

 

[SQLGeek]

It's no fun that way.

Imma do it anyway.

 

[Buckshot Wade]

Did I miss something here?

 

[SQLGeek]

Did I miss something here?

Sorry, acting my shoe size instead of my age.

 

[Big Green]

I believe Geissele has a video that describes why exactly. But It has to do with the way the threads are cut into the metal and the strength of said threads. Mil spec is a more expensive procedure, hence comm is cheaper and why it was more common after AWB sunset. Now I hardly ever see comm tubes or stocks. Gotta be tactical, ya' know.

 

[Buckshot Wade]

Yup, from a purely practical standpoint the thicker walls of the tube would be stiffer. Much like with aluminum arrows, thicker walls of the shaft makes for a stiffer arrow. Makes sense to go with a Mil-Spec buffer tube here of course.

One thing I'll need to pay attention to is the threads involved in the remove/replace on this weapon. The upper & lower are made of a carbon fiber & polymer blend. Damn sure want to avoid even the slightest misalignment in the installation.
But I'm very patient and never force things or try to "gorilla" my way through my working with tools and equipment. I'll be fine.