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LeftyTwoGuns
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Posted: 8/16/2009 8:14:29 PM
Can anybody enlighten me as to the differences between a carbine length Mil-spec buffer tube and a Commercial one? Thanks
mds2004
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Posted: 8/16/2009 8:16:46 PM
Commercial is slightly larger in certain areas. You are supposed to buy the appropriate buffer tube and stock depending on your lower.
What brand lower do you have?
HRoark
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Posted: 8/16/2009 8:19:34 PM
[Last Edit: 8/16/2009 8:22:14 PM by HRoark]
Originally Posted By mds2004:
Commercial is slightly larger in certain areas. You are supposed to buy the appropriate buffer tube and stock depending on your lower.
What brand lower do you have?


No, the threads are the same, or very similar, on the both commercial and mil spec receiver extension and the lowers. It doesn't matter which brand the lower is, both will fit.

If you're building from scratch, all that matters is the stock and the extension are both either com. or mil spec.

I have mil-spec extensions on all my ARs.

LeftyTwoGuns
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Posted: 8/16/2009 8:28:08 PM
I'm building from scratch and the buffer tube is the only thing that I haven't bought yet/ put much thought into. Just wondering if one was better for one thing than the other. Pros/Cons etc. What's the purpose of having the two differenet versions?
HRoark
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Posted: 8/16/2009 8:32:17 PM
[Last Edit: 8/16/2009 8:35:13 PM by HRoark]
Apparently the commercial are easier to make or something, I want to say there was a thread somewhere a few weeks ago that was pretty educational, I remember it had a drawing with the different dimesions of the different types.



Edit:

Here's the thread I was thinking of
rageracing
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Posted: 8/16/2009 9:26:51 PM
Everybody makes a stock that fits a mil-spec tube. NOT everybody makes stocks for a commercial tube. Just keep that in mind.
CTbuilder1
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Posted: 8/16/2009 9:37:46 PM
There are no pros to a commercial buffer tube at all. If you are buying from scratch I would strongly advise that you go with a milspec tube.
Primos
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Posted: 8/16/2009 9:48:07 PM
Mil spec tubes are slightly smaller in diameter. Both will fit all of the lowers out there.

That aside, I've only run into fitting issues with milspec tubes, especially with Vltor Emod stocks. They're often wayyy too tight on the tube, and will get stuck on the threads.
I've never run into fit issues with a commercial tube.
Just my experience.
ZippyGaloo
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Posted: 8/16/2009 10:16:34 PM
[Last Edit: 8/16/2009 10:28:21 PM by ZippyGaloo]
If you go with a commercial version, I would suggest doing what I did and buy the ACE Super Heavy Duty M4-7 Receiver Extension Tube. It's a much more robust and thicker tube than a mil-spec receiver extension tube (see photo). Plus it extends all the way to the lower receiver (without slanting up) creating a very solid and sturdy tube. It also comes with a sling mount, 7 positions and a stop screw (to hit a specific position every time). You are limited to the stock that ACE offers for it (which looks like a mil-spec version), or you can get the commercial version of the Magpul CTR (which is what I did), or the commercial version of the VLTOR EMOD.



CTbuilder1
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Posted: 8/17/2009 7:30:06 AM
Originally Posted By ZippyGaloo:
If you go with a commercial version, I would suggest doing what I did and buy the ACE Super Heavy Duty M4-7 Receiver Extension Tube. It's a much more robust and thicker tube than a mil-spec receiver extension tube (see photo). Plus it extends all the way to the lower receiver (without slanting up) creating a very solid and sturdy tube. It also comes with a sling mount, 7 positions and a stop screw (to hit a specific position every time). You are limited to the stock that ACE offers for it (which looks like a mil-spec version), or you can get the commercial version of the Magpul CTR (which is what I did), or the commercial version of the VLTOR EMOD.

http://riflestocks.com/catalog/images/carret-stop.jpg
http://riflestocks.com/catalog/images/m4-7ret_comp.jpg
http://riflestocks.com/catalog/images/carret7.jpg


Just because something is thicker doesn't mean it is stronger.
RLR350
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Posted: 8/17/2009 8:50:13 AM
[Last Edit: 8/17/2009 8:51:29 AM by RLR350]
All lowers are threaded the same - you won't find a stripped lower that is designated "commercial" or "mil-spec". You will see built lowers that already have an extension installed that is a particular size. For example if you buy a factory built RRA it usually has a commercial extension. So when you look for a new stock, you would want to buy the commercial size.

Since you have a choice, a mil-spec extension has some advantages, but either would work. Buy the stock that matches the extension you choose. (mil-spec extension = mil spec stock, commercial extension = commercial stock.) The mil-spec is supposed to be stronger, although you may not use the rifle in a way that you would ever notice. There are more stocks available for mil-spec. Some have optional butt pads that work best on mil-spec extensions. The Magpul extended butt pad is an example, it works best on a mil-spec CTR/MOE/ACS. It will work on the commercial versions, too, but you can't close them all the way.

The Ace mentioned above is probably nice and strong. The attachment is not a standard end plate/castle nut so you are limited on the receiver end plate you can use. This will limit your choice of sling attachment options. It is also expensive.

Not to confuse you, but you can unintentionally put a commercial stock on a mil spec extension, it will be loose and not ideal - not recommended. A mil spec stock will not fit a commercial extension because it (the stock) is too small.

The picture in the link posted above is a great visual of the differences between the two.
ZippyGaloo
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Posted: 8/17/2009 6:08:58 PM
[Last Edit: 8/17/2009 6:11:28 PM by ZippyGaloo]

Originally Posted By CTbuilder1:
Originally Posted By ZippyGaloo:
If you go with a commercial version, I would suggest doing what I did and buy the ACE Super Heavy Duty M4-7 Receiver Extension Tube. It's a much more robust and thicker tube than a mil-spec receiver extension tube (see photo). Plus it extends all the way to the lower receiver (without slanting up) creating a very solid and sturdy tube. It also comes with a sling mount, 7 positions and a stop screw (to hit a specific position every time). You are limited to the stock that ACE offers for it (which looks like a mil-spec version), or you can get the commercial version of the Magpul CTR (which is what I did), or the commercial version of the VLTOR EMOD.

http://riflestocks.com/catalog/images/carret-stop.jpg
http://riflestocks.com/catalog/images/m4-7ret_comp.jpg
http://riflestocks.com/catalog/images/carret7.jpg


Just because something is thicker doesn't mean it is stronger.



In this case it is thicker and it is stronger.
CTbuilder1
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Posted: 8/17/2009 10:58:03 PM
The walls can't be any thicker than a standard com spec tube. Otherwise a) the stock wouldn't fit on the outside or b) the buffer wouldn't fit on the inside. I've yet to see an item from ACE that was really all that impressive. A forged milspec tube with an LMT SOPMOD stock > anything in the commercial variety.
ZippyGaloo
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Posted: 8/18/2009 1:09:27 AM
[Last Edit: 8/18/2009 1:09:45 AM by ZippyGaloo]
The M4-7 is in fact thicker on the bottom forward most part (look at the photo). In my opinion ACE makes some great products. I personally own one and believe it to be a better product albeit with some limitations (i.e. available stocks and sling mounts).
JaxChris
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Posted: 8/18/2009 1:19:32 AM
[Last Edit: 8/18/2009 1:27:02 AM by JaxChris]
Yes, the stock has a thicker base along that seem - but - a receiver tube's 'weakest link' is the thinnest spot around its circumference. Since the rest of the walling in that tube is just as thin as any other extension means it has the same vulnerability as any other when taking blunt impact. If the entire tube body was thicker inside all around then I would definitely jump on it as an improved part.

ACE just had to make that area thicker to support a full spread for 7-positions instead of the typical 6. It wasn't done for overall tube strength.


john575
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Posted: 8/18/2009 1:51:05 AM
So if I have a commercial tube can I buy a mil-spec tube and use the same spring and buffer? Or do I need to buy all new components for the mil-spec tube?
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JaxChris
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Posted: 8/18/2009 2:49:48 AM
Same spring and buffer work in both. Tubes alone are 10-20$, goto a gun show to grab one for 10-12$ out the door if there's one nearby.
ZippyGaloo
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Posted: 8/18/2009 3:32:52 AM
[Last Edit: 8/18/2009 3:37:40 AM by ZippyGaloo]
It has less vulnerability along the base vs a mil-spec, so that area is not equally factored into the weakest link of the mil-spec. Basically it has a better weakest link vs mil-spec.

ACE made that area thicker for overall tube strength.
survivalshop
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Posted: 8/18/2009 10:35:37 AM
Originally Posted By john575:
So if I have a commercial tube can I buy a mil-spec tube and use the same spring and buffer? Or do I need to buy all new components for the mil-spec tube?

If you already have a receiver extension ,why buy another ? (unless you have a full stock version & want to go to a collapsible type )There is nothing wrong with a commercial tube .

I think some go over board with this "Mil spec " stuff. I looked into some of this when I put the lower together for a 308 build & some of the stuff you read here may have some some fact to it ,but until I hear from a actual manufacturer that makes both types ,its just hear say . The fact that the comm. RE is 0.020 " thicker in dia , Because its thicker ,it can have threads cut into it the conventional way . ( a thread cutting die ) Some may say its a cost cutting step , but one that is done with just about every thread cut for a threaded part out there . They say the Mil spec are forged( I have not seen any manufacture say they are , yet )they could be. That may be the reason they say the threads are rolled into them or is it because of the way the RE was made or it could be because of the thickness of the material itself.
I believe the Mil spec RE was made to reduce weight for a Rifle that was putting on weight with all those nice star war gadgets that were put on there . I chose the Commercial version , because of the extra thickness of the RE & what I have seen, in the deeper full-er cut threads .

If the Mil spec is stronger ,I want to hear it from those who tested it .

DSZM4
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Posted: 8/18/2009 2:57:33 PM
The Mil spec tube has stronger threads because of the smaller diameter compared to a comm tube.
cordovamx
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Posted: 8/18/2009 3:09:21 PM
sorry to thread hi-jack but with the commercial tube having the slanted back end and the mil-spec having the flat back would the commercial tube lead to increased buffer spring wear because the spring is being pressed against a slanted area and not a flattened one? I know, dumb question but I was curious...
GearHead_1
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Posted: 8/18/2009 4:51:33 PM

Originally Posted By ZippyGaloo:
It has less vulnerability along the base vs a mil-spec, so that area is not equally factored into the weakest link of the mil-spec. Basically it has a better weakest link vs mil-spec.

ACE made that area thicker for overall tube strength.

Just out of curiosity, have you ever known anyone to break a receiver extension that wasn't either in a combat situation or abusing it?
markm
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Posted: 8/18/2009 5:04:24 PM
Originally Posted By CTbuilder1:
There are no pros to a commercial buffer tube at all. If you are buying from scratch I would strongly advise that you go with a milspec tube.


But you get to tell people with the correctly spec'd part that they're SNOBs. That's a pro to some of our more childish members.

The last time this came up, the specifics of why commercial re's are inferior were clearly stated, and some peckerwood still chimed in and said it was a snob issue.
We need to get over the romance of carrying a 1911 pistol, and get on to the business of shooting smelly bad guys in the face with a modern handgun.
markm
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Posted: 8/18/2009 5:08:13 PM
Originally Posted By GearHead_1:
Just out of curiosity, have you ever known anyone to break a receiver extension that wasn't either in a combat situation or abusing it?


A subject matter expert on a more knowledge based gun board sited seeing a few commercial re failures. All of the failures he saw happened where the re threads into the receiver. The threads not properly engaging the lower receiver is one of the main weakness issues with commercial re's.

We need to get over the romance of carrying a 1911 pistol, and get on to the business of shooting smelly bad guys in the face with a modern handgun.
markm
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Posted: 8/18/2009 5:09:36 PM
Originally Posted By survivalshop:
There is nothing wrong with a commercial tube .


For some folks this may be true. I would NEVER have one on any of my guns.

We need to get over the romance of carrying a 1911 pistol, and get on to the business of shooting smelly bad guys in the face with a modern handgun.
45FMJoe
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Posted: 8/18/2009 5:51:53 PM
Originally Posted By markm:
Originally Posted By survivalshop:
There is nothing wrong with a commercial tube .


For some folks this may be true. I would NEVER have one on any of my guns.



When I point this out in "Tier 1 vs the rest" debates people call me all sorts of names.
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