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Discussion Starter · #1 ·
Can a mil-spec buffer tube fit on the threads of a stripped rock river lower? Thanks
 

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My understanding is that all buffer tubes will work on all lowers. Also all buffers will work in all buffer tubes. The problem is the larger com buffer will not allow the smaller mil spec stock to fit on it.

If that is not enough help. RRA does list com or mil spec buffer tubes as a option on their site.
 

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Why 2 sizes of buffer tubes?

:headscratch:
 

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Arent they made from different quality materials? I believe the mil-spec has a greater ability to withstand force.
 

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Why 2 sizes of buffer tubes?

:headscratch:
I thought one size goes for A2 straight stocks and one goes for M4 style collapsible stocks.
 

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I thought one size goes for A2 straight stocks and one goes for M4 style collapsible stocks.
An A1 or A2 stock uses a rifle receiver extension, it is longer than a carbine extension, has no holes, and there is only one type.

A collapsible stock uses a shorter carbine extension, in which there are both commercial and mil-spec varieties.
 

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Arent they made from different quality materials? I believe the mil-spec has a greater ability to withstand force.
They are, both made out of aluminum but mil-spec is made out of a forging. However the (very slightly) larger size of the commercial tube has little to do with the type of aluminum it’s made out of and everything to do with a cost saving measure of omitting the extra profiling machining operation.
 

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A collapsible stock uses a shorter carbine extension, in which there are both commercial and mil-spec varieties.
Yes, carbines with collapsible stocks, why 2 different tubes???


:headscratch:
 

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They are, both made out of aluminum but mil-spec is made out of a forging. However the (very slightly) larger size of the commercial tube has little to do with the type of aluminum it’s made out of and everything to do with a cost saving measure of omitting the extra profiling machining operation.
I couldnt remember if it was a material or process difference. I do know the mil=spec is much stronger than the commercial. I believe the mil-spec has a tencil strength of 75 pounds.
 

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Discussion Starter · #14 ·
So now I'm very confused. Will the mil spec tube threaded end fit into the rra lower? The threaded hole is about 1.3 inches across.
 

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So now I'm very confused. Will the mil spec tube threaded end fit into the rra lower? The threaded hole is about 1.3 inches across.
Yes, you can use any tube you like on your RRA lower.
 

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:crying:
So now I'm very confused. Will the mil spec tube threaded end fit into the rra lower? The threaded hole is about 1.3 inches across.
The lower receiver threads are standard, they will accept both mil-spec and commercial extensions. The difference is the threads on a commercial extension do not fully engage the threads on the lower, a mil-spec does.
 

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Thread dimensions are the same.

True milspec material is 7075 T6. Many commercial styles use 6061 with nearly half of the tensile strength. This does not mean that all milspec sized tubes are automatically going to be 7075 T6.

The milspec tubes were originally had their threads cut in with a lathe and then the tubes were actually shaved down in dimension. Now the threads are rolled in.

The original commercial tubes were extrusions and the threads lathe cut. However the tube diameter was not reduces to milspec tube dimensions and were left at 1.170 and has remained as such.

So if you look at the picture above you will notice that the milspec thread engagement diameter is 1.185 or actually larger thread diameter than the commercial tube.

Since receivers are all cut to accept the milspec size of 1.185 what this means is that commercial tube threads have a slightly lesser engagement area. In the real world this means little but there are people claiming to have commercial tubes pulled out of the threads. I might think this is more due to actual out of spec construction and those tubes were more undersized than the commercial tube norm. As we know any company can build anything.
 
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