Choosing an AR15 stock starts with the buffer tube. If you have a commercial buffer tube you will need a commercial stock and if you have a mil-spec buffer tube, a mil-spec stock is what you need.
With that in mind, you can put your thoughts to some particulars for the right stock to complement the buffer tube.
Choosing the Right AR15 Stocks for your Setup
The intended purpose of your AR 15 rifle should be a major part of determining the right stock. A sniper setup will definitely have an entirely different set of stock requirements compared to a CQB AR15 rifle.
Take the Magpul PRS Precision Adjustable Stock as an example, this stock is clearly made for the sniper setup, vs most AR15 stocks that are made for close-quarters usage.
Slings also have something to do with purpose and some stocks feature built-in attachment points. The way you want it set in a sling should be kept in mind. Check out AR15 stocks with several possible placements like the Ergo F93 AR15 ProStock 8 Position Collapsible Stock.
The better a stock fits one’s form, the better it will be when the action starts. It should be perfect when shouldered and conform to your cheek and body position when you are sighted on a target. Some are even simple solutions like the manual positioning of the cheek rest.
Adjustable or Fixed
Adjustable (AKA collapsible) stocks are by far the most popular stocks for the AR-15, though the fixed stock has its audience. Collapsible stocks typically have between 4 and 8 different positions, which allows you to adjust the length of the stock to your height, shooting style, and portability requirements.
Fixed stocks are a little more sturdy, and are often cheaper. The new designs for the fixed stocks like the Magpul MOE Fixed Carbine Stock have a few tricks up their sleeve but the Mako AR15 Stock with Shock Absorber does offer more in terms of adjustments and more.
Partly associated with the weapon’s purpose, some AR15 stocks will work on a particular length really well and be a poor performer on others. This is even true with adjustable stocks. This is also relative to the user, and adjustable (collapsible) stocks offer the best versatility for a variety of users.
The balance of the weapon can become a critical factor in performance, and the stock’s weight along with the placement of other tactical accessories play a part in this. For example, when you have a longer handguard, a heavier stock can actually help balance the weapon. Different materials, design and construction can also mean wide variance on weight. so keep this in mind when looking at stocks.
The material of choice is pinned on the weight concerns as well as durability. Polymer is the most popular choice when it comes to weight and the Magpul MOE Carbine Stock is an example of this.
Additional storage may be required and quite commonly you will have it on the stock, just like on the Magpul STR Storage Stock. This storage is especially handy for storing batteries for your optics, lights, and lasers. You can also store small repair parts like a firing pin, or even a couple of rounds of ammo!
Some stocks (specifically collapsible stocks) are not legal in some places, so wherever you are, this matter needs to be looked into. The stock may be the perfect one but it may not be legal where you are - bummer.
Legal concerns aside, a large part of choosing the right stock for your AR15 comes to purpose and personal fit. In the end, what you intend to do with your AR15 becomes a big part of choosing and determining the right stock. Personal preferences or the way this stock fits and feels for you is secondary, but it is no less important. You and your weapon are one, take stock in this idea and it should make it an easier choice.