Author Topic: Mil-Spec vs. Commercial Diameter Buffer Tube ??  (Read 31066 times)

billt

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #10 on: January 02, 2012, 07:24:45 PM »
If there is .015" difference at the thread diameter, (1.170 / 1.185), how can they both fit into the same lower?

bafsu92

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #11 on: January 02, 2012, 08:57:11 PM »
If there is .015" difference at the thread diameter, (1.170 / 1.185), how can they both fit into the same lower?
As far as I know the only difference is in the shaft diameter, not the threads. I only purchase Mil-Spec tubes for all my builds (at least 25 different brands of lowers) and I've removed commercial tubes and installed Mil-Spec tubes in their place many times as well.
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tombogan03884

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #12 on: January 02, 2012, 09:55:17 PM »
Diameter doesn't mean that much if you allow for varying percentages of thread contact.
To use a common thread for an example, according to the chart in the "Machineries Handbook"
(27th ed. pg 1737 )
A 1/4 - 20 thread Class 1a has a major diameter of 0.2489 with a .0011 allowance.
But a Class 3a has a major diameter of .2500  with .0 allowance

billt

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #13 on: January 03, 2012, 06:52:19 AM »
A 64th on the diameter of a fine thread like that would make a big difference I would think. Unless that drawing is incorrect. I can see a difference in the tube diameter where the stock itself fits on, but not in the thread size. That's what I noticed when I miked the tube on my Bushy. It was smaller at the threads, larger further down the tube.

bafsu92

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #14 on: January 03, 2012, 10:04:02 AM »
What's made me always assume the thread is the same regardless is I've never seen a castle nut specified as Mil-Spec or commercial, they just sell castle nuts.
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"Political Correctness is a doctrine fostered by a delusional illogical liberal minority and rabidly promoted by an unscrupulous liberal press,which holds forth the proposition that it is entirely possible to pick up a turd by the clean end." - Unknown

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #15 on: Today at 06:24:32 AM »

Timothy

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #15 on: January 03, 2012, 10:24:41 AM »
First off, I'm not an AR guy and don't own one and have never seen the buffer tube on one.

This is from the AR something or other...

The biggest differences between the two tube types are:  1) The buffer tube diameter itself 2) The diameter of the threads in relation to the diameter of the tube.

Mil-Spec: On the mil-spec buffer tube… the threads at the front are actually a larger diameter than the rest of the tube itself.  In manufacturing, a large tube is used and threads lathed as normal. Next, the rest of the tube must be milled down to the military specified diameter.  I’m guessing this step requires more work / precision… and costs more.

Commercial-Spec:  In manufacturing, you begin with a tube that matches the final tube diameter.  The threads are cut into the front end with a lathe just like any other threaded pipe.  I imagine this to be just like the copper water pipe used in my house.



Tubing is measured by it's ID which is constant (to a point) and can have a tolerance OD of "x" depending on size and the wall thickness can have a tolerance of "y"!.  These two variables can effect the strength of the tubing involved.  From what I can tell, the threaded portion is common to both diameters which explains why there is only one castle nut available.

billt

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #16 on: January 03, 2012, 10:45:54 AM »
To me the Commercial sized tube just makes more sense based on that. I've never heard of anyone breaking either.

Timothy

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #17 on: January 03, 2012, 11:05:08 AM »
Are there two different buffers and springs available or are they interchangeable?

Just curious as it would seem that the ID is more critical than the OD for operation.  The OD of the buffer tube would effect different stocks that would fit I'd expect.  The other thing I can see is that the Mil-Spec tube has a slanted ass end to it to more closely match the shoulder angle of a stock.

Correct me if I'm off here...

billt

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #18 on: January 03, 2012, 12:18:14 PM »
You would think someone would manufacture a sleeve of some type that would make up the difference between the 2. They sure seem to have issues standardizing the simplest of things with these rifles.

Timothy

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Re: Mil-Spec vs. Commercial Diameter Buffer Tube ??
« Reply #19 on: January 03, 2012, 12:23:55 PM »
Again, I don't know squat about these guns but my SIL just did an AR10 build starting with an Armalite lower.  He bought a bunch of stuff only to find that none of it fit properly and after numerous returns and speaking with whomever he bought the lower from, he ended up having to buy nearly everything from Armalite to complete the build.

His cost to build was more than he would have paid for a stock Armalite with a flattop upper, less the bull barrel he used.

He was pretty pissed at that point.

Nice rifle but it's not a plinker by any means.  Damn thing weighs nearly 15 pounds.

 

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