This sounds like the dictionary but the only way I can
describe a frosted bullet is to say it has a surface that
looks like frost on a window pane.
The title image on this page is the worst case of a
frosted bullet I have ever seen. It will be reproduced
below with comments on how it was produced.
Frosting is frequently described as being caused by the
mold or the metal or both being too hot. I do not believe
this is true. I believe that frosting is always caused by
the mold being too hot - regardless of the temperature of
the alloy. It is of course obvious that if the metal
is hotter, the mold will get too hot much quicker than if
the metal is cold.
The above example of a frosted bullet was created
during a mold break-in session. I was having a lot of
trouble getting wrinkle free well formed bullets.
determined to eliminate temperature as a cause once and
for all. I didn't think temperature was the cause but I
wanted to prove it.
I started with the mold at room
temperature and the metal at 650 degrees. I began
filling the six cavity mold and dumping it as fast as
possible without being reckless.
I didn't time it
but the cadence was about two fillings per minute.
After about 8 fillings the sprues were hardening and
frosting over about like they would in a normal production
run. I didn't count them but the bullets began to become
show frost after about 15 fillings. At this time, the
sprue hardening was more or less normal, maybe a little
After ten or 15 more fillings the sprue
puddle was completely liquid and would pour off the top of
the mold if I removed it from the mold guide immediately.
The bullets were completely frosted at this point.
After about ten more fillings, the sprue puddle was so hot
it took a full 15 seconds to solidify and four or five
more to harden enough I could tap it with the edge of my
spoon without cutting it. It was at this point that the
featured bullet was produced.
Note that the metal temperature was 650 degrees.
This is what this bullet should look like.
It is smooth and fully formed. Note that
unlike most conventional bullets the lube rings
are round, not flat on top.
conventional bullets, the first thing I look for
when it falls out of the mold is rounded tops on
the driving bands. If they are rounded, the bullet
is immediately scraped off to the reject pile.
These bullets take a little "getting used to."
This bullet was produced at the time the
frosting was just becoming severe. This
is what frosting looks like.
Note this is
severe frosting of the entire bearing surface of
the bullet. Most frosted bullets have only a
fraction of this much frosted area.
This is the featured bullet
showing extreme lack of fill out due to severe
This bullet weighs 233 grains.
the normal weight for this bullet with this alloy
is 241 +/1 one grain. The front band of this
bullet measures .429/.430 It should be .430/.431.
The base band is a different matter. It
Just for kicks. I pushed
this bullet through a .430 sizing die with my
In some cases, very light
frosting does not inhibit fill out and the
slightly frosted will still be fully formed.
This is the lee .30 caliber bullet 309-170-F.
These were cast very fast at the end of a
casting session for the purpose of these photos.
The mold was so hot that after filling and
removing the mold from under the bottom pour
pot, 5 seconds later the sprue puddle was still
liquid and could be poured off the sprue
plate. Bullet number four, third from left was
poured earlier in this casting session and is
representative of normal castings with this
Bullet number one and two ( from the left)
were so hot when they were dropped from the mold
that they "soldered" together. If you expand
the image, you can see a flaw on bullet number
two where I pulled them apart.
The average diameter of the frosted bullets
is 0.0007 less than the diameter of bullet
number four. This difference in diameter is not
measurable in weight and if the bullets are
sized, will disappear completely. The average
diameter of the as-cast bullets is .3123. The
average diameter of the severely frosted bullets
is .3116. The largest measurement from the
frosted bullets was smaller than the smallest
measurement from a normal bullet.
|Frosting is caused by the mold temperature.
The temperature of the metal has very little to
do with it. It does cause the mold to get hotter
faster so it can be a contributing factor but
the ultimate cause is mold temperature.
These two bullets were cast from the same pot of
metal from the same cavity of the same mold.
The purpose of the experiment is to show that
bullet frosting is caused by mold temperature,
not alloy temperature.
The bullet on the left was cast from metal at
500 degrees. The bullet on the right was cast
from metal at 850 degrees.
As the pot heated up, bullets were cast at:
500, 550, 600, 650, 700, 750, 800, and 850
degrees. While the pot was warming up, the mold
was set aside to cool with the blocks open. This
was ambient air cooling. No water, no fan.
Just setting on the table with the blocks open.
The alloy was 80% wheel weights and 20%
Temperature was measured with the NOE
There is no difference in the level of frosting.
The same level of frosting was observed at all