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Old September 25, 2011, 02:24 PM   #1
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Crimped primer pockets?

Is it absolutely necessary to remove the primer pocket crimp on 5.56 brass? Reason I ask, a guy next to me at a range session a month ago was shooting various brands of new ammo in a AR15. He shot about 200 rounds then packed up and left, leaving all the brass. Being the scrounge that I am, I picked up about 50 pieces of the best looking stuff. Got it home, cleaned, deprimed. I started priming it the other day and noticed a few times the primers took a bit more pressure to press into place. I looked, and found that I had primed 5 pieces of NATO brass. Marked LC 10 with the little circle cross. I presume this is Lake City brass made in 2010? So now I have 5 pieces of primed NATO brass that didn’t have the crimp removed. Trash it or shoot it?
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Old September 25, 2011, 02:37 PM   #2
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I started priming it the other day and noticed a few times the primers took a bit more pressure to press into place.
Thats the reason you have to remove the crimp. There is not much one can do about that, you can get crimp remover or swager.
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Old September 25, 2011, 09:26 PM   #3
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So why did you only pick up 50 rds? I would have got it all. As long as your primers are seated properly they are OK to shoot. Next time get a simple primer pocket reamer or a swager. It will make primer seating a lot easier.
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Old September 26, 2011, 12:40 AM   #4
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Some crimps are more pronounced than other. I think we've all succeeded at accidentally priming a case with the crimp still in it at one time or another. Sometimes the primer will crush and sometimes it will seat, albeit stiffly. It is hard on the primer, though, with the extra seating force tending to crack the priming mix and make ignition more irregular.

You may be able to tell with a chronograph, as that crushing is often reflected by increased velocity extreme spread. More often, groups just open up some because some rounds are going off right away while others are hesitating 10 or 20 milliseconds. It doesn't sound like much, but that's a big addition to normal lock time, and lets vibrations and muscle contractions move the muzzle further of POI than when ignition is immediate.

The other common problem, even if the crimps were light, the higher seating resistance causes it to feel like the primer is fully seated when it isn't. That leaves a high primer, which can promote slamfires. Not safe in a gas gun with a floating firing pin.
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