Carbines such as the AR-15 and the M4 have many different options for customization these days. Among firearm parts, your choice of stock may well be the most vital modification that you bring to the firearm. Most ARs are sold with a standard stock of the fixed variety, which scores decently in terms of durability and stability. That said, adjustable and collapsible alternatives on the market often outclass the standard stock in terms of features. Regardless, the following variables need to be considered when choosing a stock for your AR-15.
Most adjustable stocks come with either 4 or 8 positions, giving you the option to find something that suits your height, shooting style, arm length, and weapon length. It is essential that you be able to comfortably rest your cheek when you have the weapon shouldered, and more importantly, the stock should be adjustable in such a way that it fits comfortably, regardless of the kind of use you intend for the rifle.
A carbine is supposed to be versatile, and works best when it is personalized to the user. You would obviously want it workable in different situations such as hunting, range shooting, or defending property. For the last, you would probably pick a collapsed stock, which is a smart choice. Meanwhile, range shooting goes better when you have a rigid metal stock fitted with the other AR15 parts. In other words, you will want to check the rigidity and durability of the stock against the use you intend for the rifle.
Commercial or Mil Spec
Lots of gun buyers skip over this aspect, but it definitely bears consideration. Find out if the buffer tube is commercial diameter or mil spec, those being 1.170” and 1.140” respectively. The difference may be small but it is significant, and can determine whether the stock cracks into the buffer tube with each shot you fire.
Are you constantly in need of extra ammo, or just prefer to be extra-prepared? Then get a stock that holds something more than the standard. Manufacturers today have tons of options that allow for additions of this sort. There are stocks that serve as multi-tools, carry extra optics batteries, hold your GPS, and more. Decide what matters to you in most cases, and aim for that functionality. As long as it is practical, you can also consider long-stretch scenarios and prepare for those as well.