Calling the AR-15 “the most popular rifle in America” would be an understatement. The AR-15 successfully implemented modern plastics and aircraft-grade aluminum during a time when most other firearms were still being built with steel and walnut. It also popularized smaller-caliber, higher-velocity rifle cartridges which forever changed the landscape of duty- and military-rifle cartridges. There is also the modularity factor. The AR-15 is probably the first successful modular rifle design whose upper and lower halves could be mixed and matched without needing special tools or equipment. To this day, this same degree of modularity allows shooters to enjoy using various length barrels, uppers or different calibers for different applications.
Many of the AR-15’s sub-assemblies are equally modular and enjoy the same drop-in nature as the firearm’s larger upper and lower halves. AR-15 trigger assemblies, for example, are one such accessory. Except for cassette style triggers, AR-15 trigger assemblies are typically made up of eight major parts: Three springs, two pins, the hammer, the trigger and the disconnector. The standard mil-spec AR-15 trigger is designed for reliability above everything else to ensure that its hammer can detonate harder primers associated with 5.56 NATO or .223 Rem. cartridges. The downside is that its trigger pull leaves much to be desired from an accuracy or finesse perspective. Upgrading the trigger assembly with one of the drop-in triggers listed here can be a good way to coax extra accuracy from one’s rifle short of having to upend and re-barrel it with a more accurate barrel.
Wilson Combat Enhanced Trigger Unit MSRP $226.95
The Enhanced Trigger Unit is Wilson Combat's most advanced modular AR trigger unit to date. This two-stage has a black DLC (Diamond-Like-Carbon) finish on essential action parts for corrosion protection and has 4-4.5 pound trigger pull right out of the box. There is a short, positive reset for fast follow-up shots and better accuracy, and the trigger housing contains an H13 heat-treated trigger, hammer, sear and sturdy stainless steel spring to ensure a streamlined installation.
Geissele SSA-E ($245 MSRP)
The Geissele SSA-E is one of the most popular drop-in AR-15 trigger upgrades. Visually, the Geissele SSA-E looks like a slightly modified version of the standard AR-15 trigger, because Geissele designed it with the same type of reliability in mind. It’s also intended to drop into any standard AR-15 or AR-10 lower receiver in the exact same manner as the original assembly. However, unlike a standard trigger, the Geissele SSA-E has a non-adjustable two stage trigger pull with a final break that’s light enough for precision-oriented AR-15 or AR-10 pattern rifles.
LaRue Tactical MBT-2S (MSRP $115)
The LaRue Tactical MBT-2S trigger is another drop-in two stage trigger similar to the Geissele SSA-E mentioned above. LaRue’s toolmaking staff manufactures each LaRue Tactical MBT-2S trigger assembly by hand from solid plates of S7 tool steel. LaRue Tactical set the MBT-2S trigger pull weights to break at 4.5 pounds in total: 2.5 pounds during the first stage and 2 pounds on the second and final stage. Each MBT-2S trigger also comes with an additional "heavy" trigger spring that increases the pull weight to 6 pounds for end users that may need the extra weight.
CMC Triggers Single Stage Flat Trigger (MSRP: $189)
The CMC Triggers Single Stage Flat Trigger is a drop-in cassette style trigger that is enclosed in its own housing and is meant for competition style AR-15 firearms, including pistol caliber carbines (PCCs). Unlike the other triggers listed above, whose trigger pull travel path has two stops before the final break, the CMC Triggers Single Stage Flat Trigger breaks after a single motion with only 3.5 pounds of motion. The flat and hooked trigger face is very popular with competitors who seek to maintain a high degree of control over their triggers and PCCs while being able to shoot very fast and controlled split shots.CMC Triggers also manufactures this cassette type trigger to specifically fit large pin lower receivers and the .22 LR S&W M&P 15-22.
Timney Triggers Impact AR Trigger (MSRP: $134)
Timney Triggers offers the single-stage Impact AR Trigger as a high-quality general-purpose aftermarket cassette-type drop-in trigger that’s designed for AR-15 pattern lower receivers. The Timney Triggers Impact AR Trigger has a non-adjustable trigger pull weight ranging between 3 and 4 pounds. As a unit, it drops right in and makes use of the existing AR-15 trigger pins that work with the standard trigger AR-15 pattern trigger assembly.
