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GUNS Magazine May 2012 Digital Edition - Page 14
STORY: Glen Zediker Making triggers better. PiN it I ’ve said many times the only real way to improve a trigger on an AR-15 is to replace it with something from the aftermarket. There used to be a scant few, now there are a many Anyone who’s read my books knows those I favor, so this work here isn’t a buyer’s guide. I have found no matter which aftermarket trigger you choose, there are ways to make it perform better, and keep it performing well. Some come supplied with their own proprietary trigger and hammer pin sets. Pin quality matters. Think about how the system functions, and how much room there is for imperfection considering receiver hole sizes and locations and trigger pieces-parts hole locations, and it’s clear the pins that fit into these holes have a say in how well the truly functional trigger parts (hammer hook and sear) establish a consistent connection, which means a consistent disconnection. When I can, I push through a set of KNS brand trigger pins. These are true and dimensionally precise. A set of locking-style pins is a nice addition. These usually have an external locking arrangement. If the pins can’t rotate then at the least the trigger and hammer will be rotating on the same spots each cycle. Unless it’s an external lock, then the snugness of the fit with the receiver holes determines whether they stay put. This is a KNS locking pin arrangement. The trigger pin has threads and a hammer pin and locking stud (above). The locking bar fits over the hammer pin stud and screws down over the trigger pin (below). Works great. oversize Pins To this end, “oversized” pins might help. Blueprint-type pins are, or should be, .154". Oversized is a scant more at .155" (usually). KNS offers a set bigger than that, and these come with a corresponding reamer to provide an exceedingly concise fit. I’m not convinced that’s the perfect magic as it sounds because I see it more as a “last resort” to get a precise match, or for use on a well-worn receiver hole. Another .001" in pin diameter usually does it anyhow. Speaking of pin sizes, some of the aftermarket trigger sets that provide This receiver block from Brownells greatly aids trigger installations because you keep both hands free. And whatever you do, do not let the hammer fall freely when you’re doing your checks. It will—not can—crack the receiver. Block it! pins make a distinction between trigger and hammer pins, and the hammer pin is larger diameter. Normally, assupplied GI parts have no difference between trigger and hammer pins. If there are pins installed in the trigger system you should pay attention to and then maintain each in its original place. The reason the hammer pin might be oversized is the same reason I routinely install an oversized hammer pin: It’s under a great deal more pressure than the trigger pin, especially as many of the competition-type AR-15 triggers have an extra stout hammer spring to speed up hammer fall. Getting the fit closer to start will help keep it closer over use. If there’s a little slop to begin, it will get worse in a hurry. Speaking of springs: trigger performance and consistency can be enhanced with better springs. If you’re using a 2-stage trigger, the trigger spring can be changed or altered, or both, to likewise change first-stage pull weight. If it’s a single stage, then the trigger spring has a decided influence on the break-weight of the trigger. The hammer spring, as mentioned, can have a decided influence on the speed of the hammer fall, which is locktime. That’s the one—well, one of the ones—main disadvantage shooting an AR-15 against a bolt gun. AR-15s are slow. There’s a limit to how much tension a hammer spring can have. Some of our government competition shooters have experienced broken hammers and radically accelerated wear from getting a little too far over the top. Function problems can also result from a too-stout hammer spring. Remember: the carrier has to set the hammer. I like and use (coincidence) chromesilicon (CS) springs. This material is world’s better than the standard music wire because it just doesn’t change. A CS spring, if manufactured exploiting this material’s potential, will last the lifetime of the firearm without any notable degradation in performance. It also rebounds faster at a (measured) lighter weight than music wire. That means the spring compresses easier and releases harder. All good. Not all aftermarket triggers can use standard-form springs, but if yours can I think it’s a wise investment to upgrade to CS. 14 W W W. G U N S M A G A Z I N E . C O M • M AY 2 0 1 2