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Old 12-02-2012, 7:24 PM
BlackMark BlackMark is offline
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I use both DPMS metal mags and Magpuls in my AR-308s. I have found the DPMS mags to be of very good construction, but the distance between the fed lips is sometimes inconsistent. Metal mags are a lot easier to tune than what you might think. A $15 Brownells feed lip tool gives you the control you need to tweek the feed lips evenly, because in most instances they need very little adjustment to relieve binding and get the bullet nose up enough to feed well. If the magazine lips are too narrow the base of the bolt carrier will bind, or worse yet slip right over the cartridge and fail to feed. The minimum spec is 0.545" between the lips and I have found references of up to 0.575" maximum. Take the bolt carrier out of the rifle and take your magazine apart. Place the base of the bolt carrier between the feed lips and see if it seats completely and passes smoothly between the lips. If not,you will need to open the lips slightly until it does. Polish all edges of the follower gently while you are at it to make sure the follower is not binding. There are other adjustments to control cartridge feed angle and to make sure the bullet nose is centered as it releases from the feed lips into the chamber, but I didn't want to get too long winded. Being able to tune your semi auto magazines gives you a real sense of empowerment, and the difference in cartridge feed smoothness from a tuned magazine is amazing. The binding from an out of spec magazine can cause all kinds of feed issues. Of course you can also just go with Magpuls, or use a Magpul as a diagnostic to see if your metal mag is the source of the problem, but if you are old school like me and like the look and feel of metal magazines, it is definitely worth the effort to learn to tune.
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