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Difference Between AR-15 Buffer Tubes

The Purpose of the Buffer Tube

The buffer tube serves two very simple purposes. First it allows an individual to attach a stock to the weapon. The second thing is it houses the buffer and buffer spring that allows the rifle to operate effectively. That’s it!

The Different Types of Buffer Tubes

There are a few items you need to know before determining which buffer tube is right for you.

6061-T6 vs. 7075-T6: 7075-T6 has twice the tensile strength of 6061-T6. Most manufactures will only use 6061 to decrease cost. You can see the difference in the strength in the chart below.

Alloy and Temper Form Tensile Strength
7075-T6 Forged 74
7075-T6 Billet 77
6061-T6 Forged 38
6061-T6 Billet 38
Note: Data taken from DOT/FAR/AR-MMPDS-01 Metallic Materials Properties Development & Standardization

 

Forged vs. Billet: This is an age-old argument that you will find numerous opinions on if you take the time to Google or look at forums. In reality this is not an argument at all. If you look at the chart above you will see that there is little to no difference in strength. The only discernable difference is that because a billet alloy is completely machined it will have cleaner more concise cuts and lines. A forged alloy can also be machined, but the amount of material you can remove is limited, as it has been cast with a specific shape. This will make the lines and cuts not as clean and concise.

Rolled vs. Cut Threading

Rolled: Metal with rolled threads is created using a process that rearranges the metal into the required shape. This process does not remove any material.

Cut: Metal with cut threads requires machining or more specifically lathing that removes material until the required shape is created.

In a study done by Birmingham Fastener Manufacturing in 2000 they measured the tensile strength for both rolled and cut threads. In this study they took four samples from each material in a controlled study and found that rolled threads are 7% stronger than cut threads.

You can view the results here.

Mil-Spec Buffer Standards

Material: Typically 7075-T6

Manufacture Process: Forged

Threading: Rolled

Pros: If you took the time to read about materials, manufacture process, and threading you will notice that the Mil-Spec Buffer tube has the best of all worlds. Plus there are more options for stocks available on the market for your assault rifle.

Cons: None

Commercial Buffer Standards

Material: Typically 6061-T6

Manufacture Process: Billet (i.e. Bar Stock)

Threading: Cut

Pros: This is a good cheap alternative to a Mil-Spec buffer tube.

Cons: There are no military standards and no quality control from company to company. Fewer options for stocks exist in current market compared to Mil-Spec.

TheARGuys Opinion

In our opinion you should always go with a mil-spec buffer tube. It allows you to choose from a variety of manufactures for the tube itself as well as stocks for your assault rifle. On top of it all the military holds companies to a strict standard if they want their parts to be used in the field. This forces companies to use better materials and manufacturing processes.

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4 Comments

  1. DPMS ? - Page 2
    Aug 01, 2013 @ 00:53:42

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  2. Calling all AR-15 experts. Higher-end brand recomendations - Page 3
    Aug 01, 2013 @ 01:01:53

    [...] is a good link on ar15 info. Difference Between AR-15 Buffer Tubes. Top right box for different sections Doesnt cover barrel or bcg's but their is plenty of info on [...]

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  3. jollyranchhand
    Jan 22, 2014 @ 23:09:35

    One thing I’d like to point out that I see overlooked in most discussions about the differences in tubes is that since the civilian tube has a larger OD and therefore a thicker wall, it will be slightly stronger than a milspec OD tube made of the SAME material. 6061 is an aircraft grade aluminum, its a good general purpose hard alloy and not easy to bend. 6061 is used for many billet AR uppers and lowers not to mention scuba tanks, boats and suppressors. The bigger problem comes when someone is making a milspec OD tube without using 7075 aluminum. What happens then is you have a much weaker tube. My understanding is the reason they use the larger ID for the civilian tubes is because they don’t want to go to the expense of rolling threads or using 7075. So, they have to use a larger OD to be able to cut the threads into the base metal. So that being said, could you elaborate on how to identify a civilian tube from a milspec tube visually? For those of us who purchased tubes before we knew any better, I have tubes which are milspec dimensions, but I doubt they are rolled threads or 7075 alloy. Since it wouldn’t be practical to ID the alloy used, is there a visual method to tell the difference between rolled and cut threads? I’ve heard that true milspec tubes neck down where the threads are formed, and then the rolling takes the thread OD back out. Is this true, and if so could you post some photos to show this? I’m asking because I would assume that if a tube is Milspec dimensions, and has rolled threads, then it’s probably the correct alloy as well (although I’m sure there are exceptions). Thanks.

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  4. jollyranchhand
    Jan 22, 2014 @ 23:18:38

    One clarification on my last comment, I said since the civilian tube has a larger OD and therefore a thicker wall, it will be slightly stronger than a milspec OD tube made of the SAME material. I say that because if someone made a civilian OD tube out of 7075, it would be slightly stronger than a milspec OD tube because the walls would be thicker. Also, rolled threads are stronger than cut threads because the process of rolling threads work hardens the metal as it forms the threads…

    Reply

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