From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Tumbler media information
Organization: Lawrence Berkeley Laboratory

In article <37998@mimsy.umd.edu> ut-emx!lizard@emx.utexas.edu 
(Tom Linsley) writes:

#Some time back I tried using Brasso on cases, but then I read someplace
#(I think it was in the Rifleman) that Brasso weakened the structure of
#the metal and should be avoided.  Something about the ammonia in it, as
#I recall.  Anybody else remember anything about this?

Ammonia worsens "season cracking" which some types of brass are subject
to.  Cartridge brass (CDA 260 which is 70% Cu and 30% Zn) is one of the
weakest alloys in this respect.  It is also subject to dezincification
which is what happens when the brass is dissolved and only the copper
is redeposited.  You see this as copper spots on the case.  Season
cracking doesn't happen if the zinc content is at or below 15% but you
need the high zinc for the tensile strength in cartridge brass.  Season
cracking occurs when the material is highly stressed and subject to
corrosive atmospheres or liquids.  After forming, cartridge cases have
lots of residual stresses; these are what's causing the problem.  You can
anneal those stresses out, though.  This gets a little too tricky as far
as I'm concerned because you want an annealing temperature low enough to
not hurt your tensile strength but high enough to kill the season
cracking.  You may get some softening at any temp above 200C and you may
not be able to get good relief from season cracking below 275C.  So it
may not even be possible.

Unfortunately, cartridge brass can't be re-hardened by heating and quenching 
as you do with steel.  Cartridge brass has to be "work hardened"; it is
made harder by "working" it which is rolling it thinner or reshaping it -
anything to break down those metal grains into smaller sizes.

       JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Tumbler media information
Organization: Lawrence Berkeley Laboratory

In article <38000@mimsy.umd.edu> bercov@bevsun.bev.lbl.gov 
(John Bercovitz) writes:
#In article <37975@mimsy.umd.edu> grl@drutx.ATT.COM (Randy Lyman) writes:

Re: drying of cartridge cases.

## [stuff deleted, obviously]
##(If they don't dry well using this method, 
##you can stick them in an oven, pre-heated to the lowest setting, 
##for several hours.  Turn the oven off before you put the cases 
##in, and place them on a towel or something non-metallic.)

#Try this oven-drying on a couple of test cases first.  A long time 
#ago I tried this and found that my oven on its lowest setting cycled
#hot enough to slightly anneal brass.  

Anyone catch my oops other than the maligned party?  No?  Well I wish
you guys would stay awake.  Randy said to turn the oven OFF before
installing cartridge cases in same.  That be good advice.  Wouldna
had the problem ifn I'd done that there thing.

          JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Brass Tumbler Media Recommendations?
Organization: Lawrence Berkeley Laboratory

In article <38065@mimsy.umd.edu> webdw@mvutd.att.com 
(Bruce D Woods) writes:
#My dad used to use an ultra-sound jewlry cleaner he got used
#from a jewelry store, fairly large capacity.  I believe the
#solution was ammonia & water.  It got the brass CLEAN without
#junk in the primer holes etc.  I'm not reloading yet, expect to
#be this winter, but am looking to get an ultra-sound cleaner.
#QUESTION:  Is their a problem with this methodology?  Does
#it work as well as traditional methods?  Comments?

Ammonia and copper alloys don't get along.  That's why steel
pipes and lead gaskets are used in ammonia-based refrigeration
plants.  It's fine to do stuff like this if the part being 
cleaned doesn't need any strength but this isn't such a case.
(I'll take credit for any sort of puns, I ain't proud.)

JHBercovitz@lbl.gov    (John Bercovitz)