AR15 commercial vs mil spec compatability

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OsOk-308

New member
Hey guys, I am starting a build on the ar15, I found a commercial stock and buffer tube kit pretty cheap, however, I am concerned as to the compatibility of these two systems. If I purchase a commercial stock kit and place it on my lower receiver are there restrictions as to what kind of upper I can get, or are all uppers the same, and the buffer tubes the only things that are different? And will either fit on my Del Ton lower receiver? Thank you guys.
 
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Technosavant

New member
There's no difference in the upper when it comes to what kind of buffer tube you use.

The only difference involved is the outside diameter of the tube itself, and that only impacts the stock you fit to the rifle. The upper is unaffected, the buffer itself and the action spring are also the same.
 
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Mobuck

Moderator
The threaded portion and internal diameter of both commercial and milspec are the same. As mentioned, the outside diameter of the buffer tube is where the dimensions differ. The buffer tube/stock has nothing to do with any other parts. Do be certain you use a carbine buffer and spring with the adjustable stock and don't go cheap on these two parts.
 
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Justice06RR

New member
How cheap is the Commercial stock kit you found? If its around $35, which I've seen at Aimsurplus, spend another $10 or so to get yourself a Milspec kit instead.

If you buy a commercial buffer tube, milspec stocks wont fit IIRC so you are limited to commercial stocks only.

Here is a decent UTG stock kit for $45 and is made in the USA. I have it on my AR and the quality is excellent!

http://vtsupply.com/utg-pro-usa-milspec-6-position-collapsible-stock-kit-ar15-m4-p-592.html
 
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Crow Hunter

New member
If you have a choice, Milspec is the better one, even if it will cost you a little more up front.

You will be guaranteed that any stock that has or will be manufactured with the military in mind will fit.

Also, rolled threads are better than cut threads for strength.

If you ever have a stubborn case and have to mortar the rifle to get it out, you have less risk of bending the tube.
 
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theunderdog1982

New member
Better not go cheap on the buffer tube though if you want "mil-spec". Don't go to ebay and buy a mil-spec buffer tube for 10 dollars because even though it says mil-spec, its probably made in china and wont even be as good as a commercial tube, sure the diameter might be different but still the lower quality materials used will moot any point in the diameter and type of threads. Buy from a quality retailer. Mil-Spec tubes can break too and if you have to mortar a case then you have problems anyway. Either tube would be ok IMO, a commercial stock isnt fragile just don't hang on it like an ape.

But if you absolutely have to bang your rifle on the ground to get a case out make sure you're stock is completely clasped.
 
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madcratebuilder

New member
The cheap mil-spec RE's are mil-spec diameter only. Not true mil-spec construction, that is forged 7075 aluminum in 1.146" diameter. You get what you pay for, a cheaper extruded 6000 series or lesser aluminum tube. Probably adequate for most users.
 
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OsOk-308

New member
Thank you for all the input. It is actually my buddy who put together buffer kits. It was more about the stock itself, I found the one that I want howeve
r the commercial version is much cheaper. But in the grand scheme of things it might not be much more expensive to go with the mil spec version. And from the sounds of things that may be the better choice.
 
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OsOk-308

New member
He does both. I just figured I'd ask if it mattered much. I put together an ar15 before, but i stuck with mil spec. I understand the size differences and that they are not compatible, i just wanted to know how important the decision was.
 
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OsOk-308

New member
He does both. I just figured I'd ask if it mattered much. I put together an ar15 before, but i stuck with mil spec. I understand the size differences and that they are not compatible, i just wanted to know how important the decision was.
 
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Quentin2

New member
I also would use a quality milspec receiver extension. I normally use BCM but recently tried one from PSA and it was good, 7075 alloy. If you're wanting a quality build use quality parts. Considering the cost of the entire rifle the extra for a proper RE is a drop in the bucket.
 
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sailskidrive

New member
The threaded portion and internal diameter of both commercial and milspec are the same.
Click to expand...

Some thing that hasn't been mentioned is that the commercial tubes are shaped differently at the rear of the tube; the commercial tubes also have a nice little lip w/ a notch that helps line up the tube and gives the buffer retainer a place to "live".

http://www.google.com/imgres?q=commercial+versus+mil-spec+buffer+tube&num=10&hl=en&biw=1280&bih=574&tbm=isch&tbnid=tkOxcN-3ReGcZM:&imgrefurl=http://gunblog.com/magpul-ctr-buttstock-review&docid=Kyp63KAZfQyN4M&imgurl=http://gunblog.com/wp-content/uploads/2012/05/ctr_stock_specs1.jpg&w=1152&h=904&ei=wFkEUIb0D6jF0AHnls2oBw&zoom=1&iact=hc&vpx=196&vpy=139&dur=3174&hovh=199&hovw=253&tx=109&ty=103&sig=111623293308920865297&page=1&tbnh=114&tbnw=145&start=0&ndsp=19&ved=1t:429,r:1,s:0,i:78
 
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Quentin2

New member
Some thing that hasn't been mentioned is that the commercial tubes are shaped differently at the rear of the tube; the commercial tubes also have a nice little lip w/ a notch that helps line up the tube and gives the buffer retainer a place to "live".
Click to expand...

Don't see this as an advantage, I've never noticed a problem in this area with the milspec RE. They go right on and work in my experience.
 
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