Piston vs DI Dilemma: The AR-15 Gas Choice
37:50 October 17, 2009
Science & Technology
nutnfancy
Direct gas impingement AR-15s suck. Wait a minute, maybe that's piston driven AR-15s suck. Now that I have your attention I'll say they're both good and each has its own pluses and minuses that need your consideration. Long proven in many battles, the DI (direct impingement) M4/M16/AR-15 series are very reliable if maintained and lubricated properly. If it were not so it never would have lasted this long in US military service and many of the "it's broke, its needs replacing now" arguments ring hollow with me. That's not to say it cant have its problems and is failure-free. In the DI design by Eugene Stoner, the introduction of cyclic gas into the receiver makes things dirty and heats up critical components. That heat can accelerate wear and possible parts failure in extended full auto fire and makes cleaning a chore. Also running shorter barrel lengths on a DI gun is taxing to the system and it often needs heavier buffer, spring, and maybe even port adjustments to ensure reliability. Count on some tweaking. Also running a suppressor off a DI gun can cause debris and powder to be blown back into the users face, even with charging handles that incorporate deflection channels. The current piston AR-15s, like the Ruger SR-556 shown, promise to cure many of these problems. They transfer the heat and dirtiness up front at the regulator/piston mechanism, keeping the bolt cooler and cleaner. From my experience at this point, piston ARs will foul in the piston/regulator area and require similar cleaning to a DI gun in this area. But they function consistently with or without short barrels and/or suppressors and promise longer intervals without lubrication or service. But it's too early to tell if they are indeed the superior system. Some early designs have shown design weakness like spring failures in the piston transfer mechanism after high round counts. Other show carrier tilt resulting in shaving of the buffer tube. But the designs are being perfected and have measurable benefits in some POUs. So far however in most like comparisons, most have not been able to surpass the DI guns in terms of light weight. As a result, most DI guns usually have a faster swing and more manageable carry weight when similarly equipped. This leads to better mobility. In POUs requiring only semi-automatic and un-suppressed fire, maybe the DI is still the best choice and I predict it will remain popular. If the user can take the added weight of a piston driven AR-15 then many will enjoy the cleaner bolt, promise of better durability, and taking the heat out of the receiver. But if weight is your most critical attribute, a quality made DI AR-15 will still serve you well. //////////////////// Music: From artists Torley Wong and Jimmy G. Most images are TNP originals. A select few are from PhotoBucket.com whose posters have specifically agreed to worldwide, unpaid distribution of their pictures by agreement to that websites Terms of Use and by selecting such distribution in their account preferences.
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