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Shoulder dents in AR15 and AR10 cases

rawhitney

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Jul 31, 2014
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This isn't necessarily a reloading question but I thought someone here might have advice. I reload .223 and .308 perfectly with cases undamaged. I am noticing about 30-50% of cases have shoulder dents after firing in an AR15 and an AR10. I suspected that the cases were being damaged by hitting the case deflecter upon ejection. Can anyone confirm this? Regardless, how do I fix this? I have adjustable gas blocks on both rifles. Should I adjust them to put less force on bolt resetting? Appreciate anyone's help!
 

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Was the brass cleaned for the photo? If fired brass has soot back to here (your photo) , slow burn rate powders & necks not sealing on firing, would be my guess.

Little to no neck tension plays a part also.

Is a suppressor being used?
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This isn't necessarily a reloading question but I thought someone here might have advice. I reload .223 and .308 perfectly with cases undamaged. I am noticing about 30-50% of cases have shoulder dents after firing in an AR15 and an AR10. I suspected that the cases were being damaged by hitting the case deflecter upon ejection. Can anyone confirm this? Regardless, how do I fix this? I have adjustable gas blocks on both rifles. Should I adjust them to put less force on bolt resetting? Appreciate anyone's help!
I've seen Dents like that from too light of a charge or necks not sealing properly, and gases being pushed onto the shoulder.
 
Hmmm sure looks like hydraulic dents from a sizing die with too much lube.
It's possible that the brass is striking the deflector on the way out and if that's the case I would lean towards it being over gassed, not really a big deal if it is.
 
Yep, either the necks are not sealing during firing, or you have lube left on the shoulder that is cooking off and causing the dents. If it were hitting the shell deflector, the dent would be horizontal, not vertical.

How many times have those been loaded and are you annealing between firings (or after every other firing)?
 

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