Yes, it's is one of several metals used to alloy for harder cast 
bullets. It's standard in lead wheelweights (which happen to be a 
favorite Pb source for the do it yourself caster).  Appropriate 
bullet hardness is a function of pressures for a given load. Hardness 
is a Goldilocks problem for the cast boolit loader.

Too soft and leading occurs at some higher velocity.
Too hard and the boolit base doesn't obturate to form a seal as it 
travels through the barrel. That allows gases to escape up the lands 
and flamecut the slug (leaving lead in the bore).
There are a variety of methods for coping with higher pressures and 
velocities.  Hardness can be increased by alloying and water 
quenching. Metal gas checks (Cu or Al) can be swaged to the boolit 
base. Some hard core old school loaders paper patch their cast boolit 
cartridges (which has the advantage of lapping/polishing their bores).

almost certainly on a DHS list somewhere... >:-}

dw

Not me but wish I was their 
neighbor...  http://castboolits.gunloads.com/showthread.php?t=26559


At 08:27 AM 1/20/2010, Robert Kondner wrote:
>Hi,
>
>  I recall that antimony was used in casting bullets. I recall it reduced
>"Fouling" in rifled barrels. It made the metal harder..
>
>Bob Kondner
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
>Sent: Wednesday, January 20, 2010 10:30 AM
>To: [log in to unmask]
>Subject: [TN] Antimony in solder
>
>Hi Technet
>A solder question today.  What is the technical difference in using a
>solder alloy containing .2% to .5% antimony (Sn63Pb37Sb.4A) versus using
>standard eutectic SN63PB37 solder?  Reliability implications?  Easier to
>solder or inspect?
>
>Thanks!
>
>Graham Collins
>
>
>
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