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GUNS Magazine Digital March 2011 - Page 24

• G L E N Z E d I k E R • BOLt CARRIER ASSEMBLy The heart of the rifle. n an AR-15, the bolt and carrier are the “action.” The upper I receiver serves to hold the barrel and give the bolt carrier a place to ride. There’s no integral relationship between the receiver and the firing mechanism. That’s different. The bolt carrier “carries” the bolt back and forth in the upper receiver. It functions to house the bolt, sure, and also to reset the hammer. The carrier also bears the brunt of the gas pressure during operation; this pressure moves it back to cycle the firing mechanism. The bolt carrier has nothing to do with headspace. That’s all in the bolt. Using the same (checked and checked off) bolt in different carriers is accepted as “safe.” Bolt carriers come in two basic configurations and then a few unique takes. The essential designs differ mainly at their back ends. AR-15 carriers have a shorter section of full diameter at its tail; the M16 carrier has a longer section. The M16 carrier has a shrouded firing pin and so requires a “large-collar” pin style. The extra collar diameter is necessary for it to be reset. When Colt did the “receiver block” to prevent owners from installing any full-auto parts, they sliced the rear of the carrier bottom slap off. Class III Parts? To the semi-automatic shooter, the differences in these carriers come down to weight. The M16 is heavier, just over an ounce. That’s good. Now, I can’t tell you to run out and buy one, M16 parts without Class III validations are a violation of the NFA. That’s Federal Law. There are some “match” carriers that possess forms virtually identical to the M16’s. This, as anticipated, is done to increase carrier weight. Some also like the shrouded firing pin because they think it’s more reliable. In a clean rifle there’s no difference. Dirty guns are unreliable, no matter which parts they’re made from. When I have the choice and when I think the rifle really “matters,” I like to have a heavier carrier, and a set that’s all it can be. That means here’s your third hand. This is the Sinclair bolt tool. Its job is to compress the ejector so it can be easily installed or removed. Works like a charm. There’s a hole in the tool that allows access to and for the ejector pin. proprietary carrier design, select bolt and on down the list of pieces, each representing what I think is the best of its kind, and mostly because it just makes me feel good. Otherwise, “good” is good enough, as long as good is not a conjecture. I honestly don’t think a “premium” carrier can make a rifle shoot any better. They are usually well Glen had a wave of bad firing-pin retainers. he bought a package of six and three were usable. The ends didn’t match in alignment or lengths and no amount of finesse could get the bad ones installed. After making sure it’s a worthy part, he polishes and “rounds” the ends of the firing-pin retainer to make sure it’s as easy as it should be to remove and reinstall. he also started using the very old-style, solid firing-pin retainers with zero problems. As often as a carrier should be broken down, such a purchase is not extravagance. 24 here’s nice. Originally designed by Dan Young and now done by Les Baer, it’s a hunk-a-hunk of pretty metal, with features. The flutes help it hold lube and reduce surface area, and the quality and extra weight suit it well for competition use. Plating makes for no-stick clean up. Speaking of, some fear the fact the plating makes the carrier harder than the upper receiver, but, guess what? Steel is harder than the upper receiver, too. Keep it all well lubricated! Bolt carrier designs are essentially limited to two formats for the back end of the carrier to take. Specifically, how much back end it has. M16 bolt carriers and most aftermarket “premium” carriers have a longer portion of full diameter. That makes them heavier. Glen likes heavier carriers. higher mass means the bolt will stay locked up a little longer. If you’re shooting a carbine or higher-pressure loads through a rifle, that’s some insurance against pressure-induced extraction difficulties, as well as against case failures from the same cause. WWW.GUNSMAGAZINE.COM • MARCH 2011

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