Monday, March 26, 2012

AR-15 Stocks: What Do I Have-What Should I Get?

A common theme in our blog posts is to concentrate on the application in which you plan to use your AR most of the time when deciding on its configuration.  An easy way to upgrade a basic AR-15 is to select a stock that will enhance the weapon’s usability and performance.  In this post, we will explain the basic differences in AR-15 stocks in order to help AR enthusiasts select the best stock for their application.

Ace M4 Socom Stock
Most AR-15 rifles come with either a fixed, A2 style stock or a collapsible, multi-position, M4 style stock.  The stock is mounted on the buffer tube that attaches to the lower receiver.  Fixed and collapsible stocks use different buffer tubes, and there are two main types of collapsible stock buffer tubes: mil-spec and commercial.  Some fixed and collapsible stocks also use their own proprietary buffer tubes (Magpul UBR, Ergo F93,  and some Ace stocks).

We often receive inquiries as to which of the two types of collapsible stocks/buffer tubes would offer the best performance.  Before there were a zillion producers and marketers of AR-15 accessories, many aftermarket stocks were only made to fit the mil spec buffer tube.  This situation either limited the choices for AR owners who had a rifle with a commercial size tube, or forced them to purchase a new mil-spec buffer tube and deal with removal of the old parts and installation of the new ones.  Most AR parts manufacturers now offer all models of stocks in their product line in both sizes.  Mil-spec buffer tubes have an outside diameter of about 1.15", while commerical tubes have an outside diameter of about 1.17".  Mil-spec tubes are minimally shorter, measuring 7.25" in length, while the commercial tubes (with the slanted back) are about 7.80" in length.

Whether or not there is a quality or performance difference between the mil-spec and commercial models of stock/buffer tubes is a matter of opinion.  Some people believe that the manufacturing processes and materials used make one better than the other; but honestly, you have to be doing something outside of the weapon’s design to have this part of the AR-15 fail or contribute to a problem.  The image we have displayed shows the actual measurements of the two buffer tubes.  While there is a minimal size difference at the thread area of the tube, both tubes will fit securely on any mil-spec lower receiver.

One way to tell if you have a commercial or mil-spec buffer tube on your weapon is to remove the stock from the buffer tube.  Typically, a mil-spec buffer tube has a flat end, while the commercial tube has a slanted end.  If you can tell which type is currently on your weapon, you can save some money by only having to purchase the correct stock, instead of a stock and compatible buffer tube.  Removing and installing a stock is a very simple process; removing and reinstalling a buffer tube, end plate and castle nut can require a little more skill and is much easier with some specific tools.

Magpul UBR-Flat Dark Earth
The main benefit of collapsible stocks is their ability to shorten the “length of pull”.  This can allow users of various sizes to comfortably shoot the weapon.  Collapsible stocks also provide reduced overall length for storage, transport, and close quarter engagement applications.  Some AR users prefer fixed stocks because they offer a quick and repeatable “cheek weld” for faster sight/target acquisition.  Stocks like the Magpul UBR and Ergo F93 have a fixed cheek position, but still collapse and extend for length adjustments--offering “the best of both worlds”.

It is important to note that some states and local municipalities prohibit collapsible stocks.  Your state's DOJ website should have this information available.  If you have any questions about stocks, selecting the right one, or anything related to the AR-15, please contact us.  Our sales/customer service team would be happy to assist you in choosing the right one to enhance the performance of your AR-15.



  1. I have what MAY be a commercial buffer tube, but the back end is not slanted, but straight, just like the military specification buffer tube. It also does NOT have all of the stop indentations. It dates back to 1982, and that may be the reason. I was led to believe that what I bought back in 1982 was a mil spec buffer tube, spring, buffer and buttstock. The buttstock itself is ALUMINUM with a textured rubber coating. I found out the hard way that present-day mil spec buttstocks will not fit my buffer. They are just a bit too small to go over the buffer tube.

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