A recent shop inventory revealed no fewer than 10 different models of AR buttstocks waiting for new homes in my parts bins. That number is small when compared to the growing variety of available aftermarket and OEM stocks. A quick perusal of MidwayUSA's well organized website shows no fewer than 80 different options for the AR-to-shoulder union. Most of the stocks on my shelf won't stay there long—they are popular models I seem to be re-ordering regularly.
While most of us don't give much thought to the buttstock once it is placed in our shoulder pocket, the truth is it contributes to effective shooting long after we assume the desired firing position. An effective recoil pad design helps hold the stock in position so there is no shot-to-shot slippage, while reducing felt recoil on large caliber ARs. An ergonomic cheek rest helps align the shooting eye with a rifle's sights and provides a place to index the cheek for shot-to-shot consistency. Many stocks have multiple sling attachment points ranging from simple slots to QD sockets. Good collapsible designs forgo exposed release levers, replacing them with protected releases to prevent inadvertent stock collapse when firing. Some of the better fixed-stock designs provide easily adjustable length of pull (LOP) and comb heights, allowing a near-custom fit.
As with any other option-saturated market, AR stock choices can leave you confused. I'm pretty complacent with things that work, so unless I see a huge increase in capability I'm not willing to foot the bill for upgrades to my personal gun stocks. Fortunately, I get to try new models all the time when testing, so I learn what does and does not work. As a custom gun builder, I make what the customer orders and only offer my two-cents when asked or when a client has no idea what to choose. The hands-down favorite models I'm asked for come from Magpul. Other companies make good stocks, but I think Magpul has a greater variety of good ones than anyone else.
There is nothing wrong with the tried and true A2 stock configuration. It is solid and will not fail unless you try to use it as a club. For precision rifle applications, however, the Magpul Precision Rifle Stock (PRS) is a clear winner in the fixed field. It is the number-one choice for precision rifle configurations on all custom orders I receive. The PRS has small hand wheels that easily adjust LOP and comb height. It also has two moveable sling attachment loops and a short section of Picatinny rail on the toe that will accommodate a monopod. The PRS is comfortable and a definite aid to placing accurate shots on target. Its main drawbacks are high cost and a size that makes it none too handy in shoot-and-move scenarios.
Magpul's CTR and MOE stocks are very popular on both custom orders and as standard equipment on package guns. Both stocks use a triangular design that protects the release. The chief difference is the CTR also has a friction lock that eliminates some (but not all) of the play in the fit between the collapsible stock and the AR's receiver extension. The CTR also offers a QD socket on either side. Price is another noticeable difference, with the CTR costing nearly double the price of an MOE. Both are comfortable and practical accoutrements that help with the shooting and carrying of tactical rifles.
Newer AR stock designs bridge the gap between adjustable fixed stocks and their simple sliding cousins. The ACE Hammer is a heavy-duty, seven-position collapsible stock that has the advantages of firmly locking to provide a fixed feeling as well as a hex screw-adjustable riser for comb height. One word of caution whenever a cheek riser is present on a collapsible stock: A standard AR's charging handle has little clearance over the top of the buttstock, so a collapsible stock with a cheekpiece may interfere with the charging handle's rearward operation. Always ensure you can operate it in each collapsible position and adjust your stock or technique accordingly.
If you're still using a basic A2- or M4-style stock, I suggest trying one of the relatively inexpensive alternatives from companies like Magpul, ERGO, Vltor or ACE. They're simple to install with basic tools, and usually yield a more comfortable fit and effective shooting tool. You might also find the increase in comfort compels you to spread the wealth by adapting your shotguns or other semi-automatic rifles to the same AR stock design, wherever possible.