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Posted: 8/31/2004 9:30:25 PM EST
I noticed just recently that some of my spent cases have slight deformation or bulging near the base or rim, approx 3/16 - 1/4" from base. Its like a "ringed" bulge. Some are not very noticeable, some are very visible, even on the same kind/lot of ammo. Headspace has been checked. barrel is an OLYMPIC 16 inches heavy barrel and has fired around 750 round. Functioning is perfect. Deformities/bulgings are very noticeable w/ ARMSCOR 5.56 ammo.
Link Posted: 9/1/2004 7:56:09 PM EST
That is a pressure ring formed upon firing in the chamber. It is from pressure devloped by the round at firing and will vary from rifle to rifle using the same ammo from the same box. Chamber, throat and bore dimensions are what cause the variations. Tighter chambers show less larger more. A .223 in theory should show less than a 5.56 chamber. However, a tight 5.56 could show less or the same (visually) than a large .223 chamber.
Link Posted: 9/1/2004 8:26:53 PM EST
If I'm understanding you right, what you are getting is the start of case head seperation. The brass gets weaker in this area as it is subjected to pressures or worked (reloaded). Basically, the brass flows forward. This is why you need to trim cases if you reload. When the brass flows, it has to come from somewhere and a ring forms near the case head of the round. On commericial brass, it is not at all unuseal to find that one firing can have the case head start to seperate.

Take a paperclip and straiten it. Make a small hook on one of the ends. Put the hook into the case and scrape it along the case wall. You will be able to feel a groove in the case where the ring is. It basically means that the case is no longer good (safe) to reload. It could mean that there is headspace issues with your rifle but if the headspace was checked, I would just suspect some high pressure rounds with weaker/thinner brass.

Hope this helps.
Link Posted: 9/1/2004 9:01:11 PM EST
Link Posted: 9/2/2004 8:42:56 PM EST
Yeap Troy Ive seen this with Federal and AE cases...some extremely bad.I stopped buying the Federal and AE because of that.I have not noticed with the UMC or Black Hills etc..
Raymond
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