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Old November 24, 2009, 09:39 PM   #1
Palmetto-Pride
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Mil Spec Vs Commercial Spec Buffer Tubes

I was wondering why the difference in the two different size tubes? I know the commercial spec is slightly larger, but I don't understand why it was ever made just a little bigger in the first place. This identification card explains the size difference http://www.magpul.com/pdfs/technotes...ffertubeid.pdf
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Old November 24, 2009, 09:58 PM   #2
NSO_w/_SIG
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It is a bit cheaper to produce from what I've read. One less step in it's production or something along those lines.
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Old November 25, 2009, 02:02 AM   #3
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Yep, cheaper to make it with extruded aluminum than Forged. Not sure why the size difference. Could be to strengthen the part due to the weaker construction, but more likely that the construction process simply lends itself to the different size better. Not sure though.
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Old November 25, 2009, 07:34 AM   #4
Bartholomew Roberts
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My understanding is the same as Rocky Mountain Tacticals - because the extrusion process is cheaper than forging, it was used to produce commercial stocks and the stocks ended up being slightly larger in diameter - either because it was necessary to give it the same strength or because of the process.

Perhaps someone who is more familiar with those processes can explain it better to us?
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Old November 25, 2009, 10:18 AM   #5
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There is a difference of .024. That is very little, so I don't think it has anything to do with the structural strength. Possibly the size of the raw material they start with??
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Old November 25, 2009, 11:51 AM   #6
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Quote:
There is a difference of .024. That is very little, so I don't think it has anything to do with the structural strength. Possibly the size of the raw material they start with??
That would be my guess. I have done a couple of subcontracts for DoD prime contractors. The military comes up with specs that sometimes make you step back and scratch your head. When you start digging, sometimes you find that the spec is completely arbitrary and there is no justification. Sometimes, the reason is an academic in nature (there are a lot of tenured professor wannabes working for DoD contractors). The other reason is that DoD contractors make more money when they don't use off-the-shelf components; they can pad their costs on a cost plus contract and that translates to bottom line profit.
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Old November 25, 2009, 12:21 PM   #7
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With milspec tubes, the threads are rolled from the tube. This results in the thread diameter being slightly larger than that of the tube itself. With "commercial" tubes, the threads are cut into the tube- since both have the same thread diameter, you need to start with a slightly larger diameter tube.

In theory, milspec tubes (properly made) have a slightly stronger connection into the receiver due to the fit of the threads, but in practice, there's really no difference. If you're out there breaking commercial tubes, I kinda doubt that a milspec one (or the rest of your rifle, come to think of it) will last all that long with you anyway.

The only real concern is you need to remember which you have in case you decide to swap out stocks.
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Old November 25, 2009, 12:54 PM   #8
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never seen a commercial buffer tube broken, but I have seen a couple "milspec" tubes fail. Although one was broken because a soldier fell on it and the other crushed by the ramp of a Stryker.

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Old November 25, 2009, 09:36 PM   #9
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So what came first the commercial size or the mil spec?
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Old November 25, 2009, 10:06 PM   #10
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Mil-spec had to have come first.
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Old November 25, 2009, 10:54 PM   #11
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I'm surprised no one has mentioned the use of different grades of aluminum alloy used in the tubes yet.

The majority of commercial tubes are made from 6061. The "better" mil-spec dimension tubes (not the $20 ones) are made from 7075-T6.

Tensile strength of 6061 = 45000psi
Tensile strength of 7075-T6 = 83000psi

That is a substantial difference the way I see it.
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Old November 25, 2009, 11:00 PM   #12
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Good point Gary. You are correct.
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Old November 25, 2009, 11:09 PM   #13
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I appreciate all the input guys, but I still don't see why the need for two different sizes.


Quote:
With "commercial" tubes, the threads are cut into the tube- since both have the same thread diameter, you need to start with a slightly larger diameter tube.
Oh wait I overlooked this. So the threads are actually the same size, so there is no difference in the receiver just the tube?
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Old November 25, 2009, 11:34 PM   #14
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If there was a difference in the threads than you would have receiver compatibility issues...
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Old November 26, 2009, 11:45 AM   #15
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Quote:
So the threads are actually the same size, so there is no difference in the receiver just the tube?
That's it exactly. The commercial tube production method of cutting the threads from a slightly larger diameter tube is cheaper, hence its use on those intended for the civilian market.
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Old October 22, 2010, 08:29 AM   #16
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mil-spec vs commercial -- not a problem

There is a $1 little gage for sale on Amazon that lets you tell which kind of tube you have. The gage is made by Tactical Intent, a company that is making buttstocks and rail covers. The gage is dirt easy, cheap and eliminates any question.

You can find it at:
http://www.amazon.com/gp/browse.html...A36ZAOEPX7I0P8
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Old October 22, 2010, 08:41 AM   #17
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There's no excuse to run a commercial RE in my opinion.... unless you have an AR that's 100 percent recreational, and you'll never use it for serious stuff.

Any RE can be broken under the right circumstances, but the strength difference between the 6000 series and 7000 series aluminums is reason enough to get the right part. Let alone that the threads don't engage the receiver as good on an aftermarket piece.
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Old December 4, 2010, 09:19 AM   #18
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http://www.calguns.net/calgunforum/s...d.php?t=153618

Post#4 will give you the dimentions and "slanted back" properties.
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Old December 4, 2010, 10:35 AM   #19
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Perhaps it may seem arbitrary to line "in line pockets" but I disagree.

One thing about the Army is vast paperwork for anything to the point of deforestation. It can get pretty barren and meaningless but it is one of those things Soldiers have to put up with like boot camp (or officer's basic course).

It's as silly as push ups, sit-ups and the two mile run at times.

Look at what they did to the .30-06 to get to the 7.62 or the .222 to get to the .223--it all seems so arbitrary!

Buried underneath the Charles Dickens guillotine carts of paperwork there is a reason more than likely to end up justifying the difference.
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Old January 29, 2013, 01:59 PM   #20
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MilSpec 1.148 vs Com 1.168 OD of the buffer tube.
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Old January 29, 2013, 08:55 PM   #21
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If I remember right, the easiest way to tell is that commercial tubes have a slanted end. Whereas mil spec tubes have a flat end.
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Old January 29, 2013, 10:20 PM   #22
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Well sig, that used to be the case but now not as much... Some commercial now have a straight end...
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