Buckle up, AR builders! Prepare for a surprising clash between stock and buffer tube combos. It’s mil-spec vs commercial AR15 buffer tubes—a thrilling showdown! Whether upgrading your AR-15 stock or embarking on an epic build, get ready for the exhilarating world of subtle differences and exciting similarities. Hold on tight for a wild ride!
Table of contents
- Understanding The AR 15 Buffer Tube
- Difference between an AR15 Mil-Spec Buffer Tube vs Commercial Buffer Tubes
- Common Buffer Tube Concerns
- Why Do Two Different Buffer Tube Standards Exist?
- Which One is Better? – MIL-SPEC VS COMMERCIAL BUFFER TUBE
- Mil-Spec VS Commercial Buffer Tube – Collapsing The Conversation
Understanding The AR 15 Buffer Tube
The AR-15 buffer tube (also known as the receiver extension), is the metal protrusion that sticks out of the rifle and serves two functions: it houses the recoil buffer mechanism, and it serves as the attachment point for the buttstock. The reason it’s referred to as a “buffer tube” is because inside the tube is a large spring (called the action spring or buffer spring), and a weighted part known as the “recoil buffer”.
More info: When the rifle is “cocked” using the charging handle, the action spring is what makes the bolt slide back forward. Also, after a round is fired, the action spring is what pushes the bolt back forward and chambers the next round. The recoil buffer sits inside the spring, and its weight provides some “buffer” against the forces of recoil. By changing the weight of the buffer, you can change the characteristics of how the rifle cycles.
Difference between an AR15 Mil-Spec Buffer Tube vs Commercial Buffer Tubes
Now that you know what’s going on inside the tube, let’s examine the differences. The most critical difference is the diameter of the area where the stock slides onto the tube. The mil-spec buffer tube is about two-hundredths of an inch smaller than the commercial AR15 buffer tube. This may not sound like much, but it’s enough that the stock that is designed for one standard will not be compatible with the other.
Other notable differences between the mil-spec and commercial buffer tubes can be things such as the angle of the back of the tube or the type of metal used. The problem is, these traits can vary by manufacturer, and are not necessarily related to the diameter of the tube or the fit of a stock.
Common Buffer Tube Concerns
If you are concerned about fitment it is recommended to purchase the stock before the buffer tube. These days most stocks and buffer tubes are mil-spec but if there is any doubt pick out the stock first. This way you have the stock you want and just need to pair it to a buffer tube.
Some stocks come in both mil-spec and commercial varieties. The best way to measure a buffer tube type is by using a caliper or micrometer and measuring the diameter of the tube. A mil-spec tube should measure about 1.146”, and a commercial will be about 1.17”. If you were to acquire a stock meant for a commercial tube you could still use a mil-spec buffer tube but it will likely be loose and have some rattle.
Why Do Two Different Buffer Tube Standards Exist?
As with so many things, it all comes down to money. The mil-spec buffer tubes were the original design, but the manufacturing processes of commercial spec buffer tubes provide a lower cost. In most cases, commercial tubes are of lower quality material (usually low-grade aluminum) and will often have lesser durability as a result.
More info: When the M4 was first introduced as a military weapon, there was only one type of tube – mil-spec. But as the M4-pattern rifles moved into the civilian ranks, companies realized that they could make the tube cheaper. By making the tube a touch larger in diameter, the threads could be cut in, vs the mil-spec tube where the threads are rolled in.
Which One is Better? – MIL-SPEC VS COMMERCIAL BUFFER TUBE
There are very few instances of the lesser quality materials coming factoring into buffer tube issues. There is little real-world evidence supporting that one standard is noticeably “better” than the other. We could take the literal “military specification” into consideration since their buffer tubes are designed with harder use and higher quality in mind. It could be argued for that fact alone that the mil-spec buffer tubes are better.
Mil-Spec VS Commercial Buffer Tube – Collapsing The Conversation
When choosing a stock and buffer tube combination, several factors come into play. Your favorite stock may only fit a commercial buffer tube, while mil-spec buffer tubes are more readily available. For most real-world cases, either option works fine. However, we here at AT3 Tactical recommend a mil-spec buffer tube due to greater aftermarket stock options and a perceived increase in strength (again, this lacks the “boots on the ground” evidence we would like to see).
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The vast majority of stocks or buffers will be mil-spec these days but if you are unsure you can measure the buffer tube if you have one or start with purchasing a mil-spec stock and then get a mil-spec buffer tube. The best way to measure a buffer tube type is by using a caliper or micrometer and measuring the diameter of the tube. A mil-spec tube should measure about 1.146”, and a commercial will be about 1.17”.
Yes, but it will be noticeably loose. On the flip side of the coin, you cannot put a mil-spec stock on a commercial buffer tube. The tube is too wide.
No. Buffers and buffer springs can be used in either one.
Since commercial buffer tubes are proprietary and non-standardized it is likely there are some that do not have a slanted back. Most, however, do.
A mil-spec tube should measure about 1.146”, and a commercial will be about 1.17”. Commercial tubes may vary by a larger degree since it is not standardized.
One Last Tip
If there’s anyone that knows the AR-15 platform, it’s the US military. As a special offer for our readers, you can get the Official US Army Manual for AR-15/M4/M16 right now – for free. Click here to snag a copy.