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skyking749
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Posted: 11/18/2009 2:20:08 PM EST
no luck in build it yourself, so I thought I would try here

I have a Vltor modstock which the receiver tube is 1.15 " diameter with flat back and peaked threads which I assume is milspec.

I have a Magpul commercial stock on a 'commercial' tube with flatter peaks on the threads (it seems) and the slanted back, but the tube measure 1.15" as well. The tube also fits in the modstock. It also has alot of play in the CTR stock until you lock the friction lock. Anyone else measured their Magpul commercial receiver extensions? I have another Rock River with a Magpul commercial kit that I will measure tomorrow when I go to my shop. I might add that there are no problems with this, I am just curious.
imortal
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Posted: 11/18/2009 4:39:01 PM EST
According to Magpul's buffer tube sizing chart, milspec tubes are about 1.14" and commercial tubes are about 1.17". If you had a commercial CTR over a 1.15" tube, that would explain the rattle. If you had a milspec CTR, I would assume that it would be seriously tight on a 1.15 tube.

I did not bother to measure my tube; my S&W M&P came with a milspec tube.
"And in this moment I will not run. It is my place to stand. We few shall carry hope, within our bloody hands."
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slappomatt
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Posted: 11/18/2009 5:36:07 PM EST
the difference in threads on mil spec and commercial are that the commercial tubes are bigger and have the threads cut down into the tube. so the width of the tube is the same as the peaks of the threads.

mil spec tubes are smaller diameter and the threads stick out from the buffer tube and the valleys of the threads are the same as the tube.
My strongest opinions are on things I know very little about. so take it all with a grain of salt! :)
skyking749
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Posted: 11/18/2009 7:21:22 PM EST
You guys are killing me. The outside diameter of my 'Commercial' buffer tube is the size of a mil-spec buffer tube but it still has the slanted back and it was bought as a commercial buffer tube. It fits in a mil-spec stock. It also fits in a commercial stock but is loose. My other commercial tube does not fit in my mil-spec stocks.
slappomatt
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Posted: 11/19/2009 3:51:43 AM EST
sounds like your stock is a mil spec size. shouldnt matter that the back is slanted.
My strongest opinions are on things I know very little about. so take it all with a grain of salt! :)
Justin-Beard
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Posted: 11/19/2009 6:09:01 AM EST
[Last Edit: 11/19/2009 6:10:02 AM EST by Justin-Beard]
Originally Posted By slappomatt:
sounds like your stock is a mil spec size. shouldnt matter that the back is slanted.

This.
Some mil tubes have a slanted back and some commercial tubes have a flat back- it's just not the norm. Regardless of how it was marketed, if your tube measures around. 1.150" in diameter and the width of the lower rail is between 0.485-0.495" then a Mil-spec ACS/CTR/MOE stock would be the proper choice.
JUSTIN BEARD
Customer Service Manager
jbeard@magpul.com