Improving an AR15 trigger ranges from total redesigns to minor changes, and here are a few not to overlook.
Last time I used all the space I had talking about the two essential AR15 aftermarket styles, single-stage and two-stage. There was more to say, and here that goes:
Most two-stage and single-stage triggers work off the existing AR15 trigger architecture, but there are those that don’t. Some are self-contained and self-defined. These “modular” triggers are all way on better than stock, to be sure. What they are, are complete housings that contain the hammer and trigger captive within the housing, installed, tuned, and adjusted as a unit (some are user-adjustable, some are not). They “drop in” and the housing is then secured by the original pins. The pins, however, don’t function within the trigger unit itself.
A modular trigger is about the easiest way to a better trigger. The question with the modulars is how well they hold up, how reliable they will be. There’s a difference in the natures, and outcomes, of stress-in-use comparing target shooting and varminting to the pounding a carbine might get in a 1000-round range session. I have not put a huge number of rounds through any of the modular units and, therefore, have no notebook references. I do, however, know a good many others who have and whose opinions I value. Consensus is that not all are 100-percent.
Many aftermarket triggers come with a set of proprietary pins, and if one does, use them. If not, a better pin set can make a difference in trigger performance.
Look at how the system operates and it’s clear that pin straightness and circumference influence trigger break and function. The pins in the standard system are also free to rotate. If the pin is a little undersized or a little bent, or both, that means engagement won’t be consistently the same each time.
And sometimes it’s not all the fault of the pins. The receiver holes also have to be what they should be. I’ve had fit mismatches from time to time, and the way to fix it is usually in the pins, because they are usually a tad amount too small. However! It’s not always a straight-up fix to purchase “oversized” pins.
One (strong) caution if you opt for “oversized” pins: make daggone sure prior to installation that the trigger parts are fully free to move as they should on the pins. The hammer, especially, should have zero drag. Sometimes a little very careful polishing on the center point area of the pin is necessary to attain a “perfect” match.
To preclude pin rotation, a “locking” pin set is the trick. Even oversized pins can move. There are a few different takes on lockers, and I put a set on all my race guns.
Better pins can also make a positive difference in modular trigger installation.
Another simple trick I do, when I can, is install a pair of chrome-silicon trigger return and hammer springs. This material is radically superior to the standard music wire used otherwise. It rebounds faster at a lighter “weight” than a music-wire-based spring. That means easier operation with no sacrifice in tension. Chrome-silicon also lasts the life of a rifle. All music wire springs will break down and lose power, so simple replacement of the hammer spring every 2500 rounds or so can be a maintenance routine item to maintain peak performance. Trigger return springs, no so much. They’re not under much stress.
A chrome-silicon replacement set will reduce trigger pull effort a tad in a stock setup, but unfortunately won’t do a thing to improve its movement quality.
An extra-power hammer spring is a commonly-used addition to a competition gun, and the reason is pretty much to reduce hammer fall time. It works. However, be warned that an extra-heavy spring can wear the receiver holes; after some time, the holes can get a little oblong and, along with it, larger. If you want to run a heavy spring, get a very well matched fit prior to installation of the spring. This stays off hole wear because there’s just no room for movement.
Lube the fool out of the trigger! Simple as it may seem, keeping the works slicked up goes a long way toward making a trigger feel better and last longer. By “last longer” I mean retain consistent feel and weight. This is especially important in a two-stage. It can’t be over-lubricated. I use light grease with boron-nitride for the engagement surfaces and hammer face (bolt carrier slides across this) and oil for the rest of it.
The only exception is for those who are out in the field in sandy and dusty conditions, or in extreme cold, and then I’d suggest one of the “dry” lubes. But some lube always!
The preceding was a specially-adapted excerpt from the book The Competitive AR15: ultimate technical guide by Glen Zediker and Zediker Publishing available from Midsouth Shooters Supply.