Subject: Ballistic Gelatin Recipe
From: khays@sequent.com (Kirk Hays)
Date: May 31 1996
Newsgroups: rec.guns

[ 
I'll copy Dave Putzolu, so it'll wind up in the rec.guns FAQ, if it
isn't there already.

Note: Ed Harris is the "C. E. Harris" of the technical section of the
_American Rifleman_ magazine.

Also the originator of "Ed's Red" homebrew gun cleaning solvent.

I take no credit for the following - I just squirrel things away.

--
Kirk Hays
NRA Life, GOA, CORE, JFPO, OSSA, OGO
]

By: Ed Harris @1:109/120.3006 via 1:2410/271 FIDOnet
 
The target material is prepared from gelatin, USP. The government
laboratories purchase this as Pharmagel A, Type 250 from the Kind &
Knox Co., Park 80 West, Plaza 2, Saddle Brook, NJ 07662.  The last
time I bought any was in 1984, and at that time the price was
$2.40/lb., or about $600 for a 55 gal.  drum, shipped F.O.B. from
Sioux City, IA.

The powder is mixed 10 percent by weight in warm, but not boiling
water until dissolved, and then poured into moulds and chilled in a
large refrigerator.  The standard block size is 15x15x30cm for handgun
bullets and 20x20x50cm for rifle bullets, but improvised moulds such
as from cal. .50 M2A1 ammunition cans work well.

You will also need Thymol or cinnamon oil as a clarifier, which is
added in the proportion of 1 drop per liter.  You will also need heavy
duty electric stirrers or an industrial mixer, moulds, a release
agent, such as Pam cooking spray for releasing the castings, LD
plastic film or Saran wrap for wrapping the blocks, a freezer for
storage if you will not use the blocks within a week, and foam coolers
to transport them to the range, if you do not have a walk-in cooler
near your lab.

To do this right, establish the tare weight of a 5 gallon stainless
steel container in which you will heat the water and mix the gelatin.
Ideally this should have a spigot on the bottom to aid decanting the
dissolved gelatin into the moulds.  Add 12 liters of water to the
container and bring the temperature to 65 degs. C and adjust the
weight by adding or deleting water to obtain 12,000 grams.  Place two
electric stirrers into the hot water, one near the top and the other
near the bottom of the container.  Add three grams of Thymol or 12
drops of cinnamon oil and stir until dissolved in the hot water. Add
1500 grams of Pharmagel A to the hot water, breaking up any lumps with
a stainless steel rod or paddle, to supplement the stirrers, as
necessary.

After the gelatin is dissolved, in 10-15 minutes, turn off the
stirrers and remove them from the solution.  Allow the bubbles and
foam to rise to the surface for 20 minutes.  If the container used
does not have a spigot at the bottom, it is necessary to skim the foam
off the surface before transferring the solution to the moulds.  Allow
the warm gelatin to stand at room temperature for at least one hour
after transferring, so additional foam which rises to the top may be
removed.

Place the gelatin in a refrigerator overnight at 0-5 degs. C.  The
gelatin may then be removed from the moulds by placing the container
in hot water.  After 15-20 seconds use a spatula to loosen the gelatin
from the sides of the container.  After two minutes remove the mould
from the hot water and invert it over a piece of plastic film spread
on a flat surface.

Once the gelatin is removed from the mould it should be allowed to
remain at room temperature for one hour, then tightly sealed in
plastic film and the wrapped block inserted into a plastic bag, which
is again sealed to prevent evaporation, which drastically changes the
consistency of the gelatin.  Once tightly wrapped, the blocks can be
stored up to six months in a freezer, or up to one week in a
refrigerator.  Unused blocks should be frozen immediately to retard
mold growth.  Before firing the blocks must be allowed to thaw and
stabilized overnight at a temperature of 5-10 degs. C, because proper
consistency is a function of the tempoerature.

Evaluation of the blocks is best accomplished by flash X-ray
photography which permits measurement of transient cavity volume as a
function of projectile striking velocity, time, distance penetrated
and projectile exit velocity energy deposit).  If high speed
photographic equipment is not available, it is useful to use a small
caliber calibration test shot, such as a steel .177 air rifle shot
from a Daisy pump-up air rifle known to give consistent performance,
which can be placed as a consistency calibration check in a corner of
the block out of the way.  The permanent cavity can then be made to
stand out well for still photography by injecting a colored water
solution of ten drops food dye to a liter of water, using as
veterinary syringe or laboratory wash bottle to reach all corners of
the permanent cavity.  To provide proper scale for the photograph, a
piece of graph paper can be photocopied onto overhead transparency
film, and used as a template to be positioned over the shot. The block
should then be placed on a light table or photographed using diffused,
backlit strobe flash.  Detailed ammunition test methodology is
available in various open-source medical and technical references.

In Home Mix We Trust, Regards, Ed