From: russ@bbxrbk.UUCP (Russ)
Subject: Re: rec.guns #8577 - Need your advice on first pistol
Organization: HASA, lost division

In article <43618@mimsy.umd.edu> boyd@mailer.cc.fsu.edu (Mickey Boyd) writes:
#Hmmm, I thought the tin/antimony addition resulted in hardness (not just
#antimony).  Thus, less tin, less hardness?  I could be wrong, as I do not
#cast myself.  However, cheaper cast lead bullets are definitely softer
#than the more expensive ones, and they also definitely contain less tin.

Sure, the tin adds some to the hardness, but not much after the 2-3%
mark is reached.  The hardness is: 7 BHN at 1%, 8 BHN at 2%, 9 BHN at
3%, 10 BHN at 5% and 11 BHN at 10% - and doesn't rise much after,
peaking at 15 BHN around 30% tin. Addition of Antimony helps more: 9
BHN at 1%, 11 at 2%, 12.5 at 3%, up to about 17 BHN at 8%, not rising
a lot beyond this point.  As you can see - Sb adds more to the
hardness than Sn for a given weight, and Sb is cheaper to boot.

The alloy I use in casting for 9mm (a relatively hot pistol load, and
particularly when I load) is based on monotype (cause I have a lot of
it) mixed with wheelweights.  Monotype is 9% Sn, 19% Sb and 72% Pb
with a BHN of about 28.  Wheelweight is the mogrel of the hand casting
family with about 3% Sb, .5% Sn and some Arsenic, the rest being lead.
At the proper mixture, this can make up a nice alloy equivalent to the
old Lyman #2 - this is good as it has the right shrinkage properties
and is nicely heat treatable.

[re: gas cutting]
#Given that the gasses are hot enough to melt lead, even perfect obduration
#would result in melting the base of the bullet somewhat, right?  Or would
#the pressure wave push the bullet out ahead of the heat?

Yes, the base of the bullet can melt.  But it doesn't touch the bore
in a large area as the side of the bullet does.  If the side melts
even a little bit you've got serious problems.  The base melting
really only happens in large charges of fast powders, and not with
slower powders (the flame temperature is lower with the slow powders).

##many cases where a soft bullet will obdurate in the barrel and get
##an effective seal where a hard cast bullet won't seal the barrel, even
##with both sized the same.
#
#In this latter case, given the same barrel, which one leaded worse?  One
#would assume that accuracy would be better given better obduration, but
#what about leading?

The harder bullet that seals better will generally give better
accuracy.  If you can cast to about .001 about the slugged bore size
you'll be set - if this is done with an allow of reasonable hardness
(say about 18 to 22 BHN) and a minimum of sizing (no more than enough
for filling the lube grooves) you'll have a nice shooting, minimal
leading load.

#Also, this seems to depend upon a perfectly smooth bore, which many guns
#do not have.  Bores can be polished somewhat by shooting them, but it is a
#fact that a rough bore will lead like hell with soft bullets.  The worst
#case of this I have ever seen was with a Taurus 9mm (I would have sent that
#barrel back to Taurus, it was ROUGH) a friend of mine owned.  The lewis
#lead remover expelled huge _slivers_ of lead from the barrel after only
#firing 100 rounds.  This were el cheapo (no "tm") brand swaged 9mm reloads.

Absolutely - a rough bore will throw all of this into nothingness.
But a couple hundred jacked rifle rounds or 500 jacked pistol rounds
will usually polish the bore nicely in most cases.  If it doesn't, you
can "fire polish" the barrel using a little kit from LBT.  I've never
done it, but hear that it can really improve the shooting of a rough
bore.

#I was actually talking about discriminating between swaged vs. cast bullets,
#for which the thumbnail should suffice.  Measuring the hardness of lead bullets
#can be done with a (rather expensive) tool, made by (I think) Briley.  If I am
#buying high velocity reloads, and my thumbnail can dent the bullet, I put them
#back on the shelf.

If you're shooting rifle or high velocity pistol, you're right to do
that.  But the thumbnail test can only tell the difference between
pure lead (about 5 BHN) and low alloys of about 11-15 BHN.  The low
alloys would be fine in most low velocity .45 and .38 loads.  (Note I
said "most" - again the fit in the bore will really count here as well
as many other factors).


If you're interested in casting bullets you might get a copy of _Cast
Bullets_ from the NRA.  It's full of interesting information collected
from the American Rifleman, and has a lot of useful techniques in
casting and loading cast bullets.  There is also a newsletter dedicated
to the handloader using cast bullets - I have information at the office
on the address and all, if requested I'll post it (this had better not
get as bad as the balistic.zip deal...)

--
Russ Kepler (posting from home)
try: russ@bbx.basis.com or bbxrbk!russ@bbx.basis.com