(Updated January 2006)
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A SIMPLIFIED 10% ORDNANCE GELATIN PREPARATION AND TEST PROCEDURE
This is the method we use to prepare 10% ordnance gelatin solution for terminal ballistics testing of personal defense ammunition. Our procedure is similar to CCI/Speer's, but it provides additional steps and guidance obtained from our own experience.
Despite cost, many people and organizations that desire to use ordnance gelatin as a test medium are intimidated by earlier published procedures, which are more complex and cumbersome than necessary. Not only is this procedure simple to follow, it provides helpful photographs and a list of sources to obtain materials and equipment required to properly prepare, preserve and cast ordnance gelatin blocks.
This procedure produces one batch of 10% ordnance gelatin solution, which consists of 9 liters of water mixed with 1 kilogram of ordnance gelatin powder, and is enough to cast a single, FBI-spec gelatin block that measures 6x6x16-inches.
Gelatin blocks can be recycled. Click here for our recycling procedure. (Requires Adobe Reader.)
Materials and equipment required:
- Using triple beam balance, measure 1 kilogram ordnance gelatin powder. Pour pre-measured gelatin powder into 3 quart stainless steel mixing bowl. Place bowl aside, out of immediate work area.
Note: If balance does not have capacity to measure 1000 grams, measure two 500 gram portions or four 250 gram portions. I f gelatin powder is scooped into a container and the container is placed on the balance, be sure to take the container's weight into consideration or your gelatin powder weight will be incorrect. Weigh the container first and add the container's weight to the desired weight of the gelatin powder to be measured. If you're measuring two 500 gram portions of gelatin powder and the container weighs 75 grams, set the balance to measure 575 grams.
Using graduated pitcher/measuring cup, measure 6 liters hot tap water (130° F ± 10° F) into 5 gallon plastic bucket.
Add 1 kilogram pre-measured gelatin powder to hot tap water while slowly mixing with paint stirrer attached to electric drill. Pour and mix approximately 1/3 of the pre-measured gelatin powder at a time, ensuring all gelatin powder is thoroughly mixed before adding more. (If you add the gelatin powder while mixing, be careful that the airflow produced by the electric drill doesn't blow the gelatin powder all over your work area. We found it best to pour about 1/3 of the powder directly into the water, and then turn-on the drill to mix it thoroughly before stopping to add more powder.) Exercise care to prevent entrapment of air in gelatin solution.
After 1 kilogram gelatin powder has been thoroughly mixed into 6 liters hot tap water, use syringe to measure and add 5 milliliters propionic acid to gelatin solution to inhibit mold growth. (Propionic acid is not necessary if you intend to shoot the gelatin block within a week after preparation and you intend to dispose of the gelatin block immediately after testing.)
Add 3 liters hot tap water (130° F ± 10° F) to gelatin solution. Slowly mix gelatin solution for 3 - 5 minutes, ensuring all gelatin powder is dissolved. Exercise care to prevent entrapment of air in gelatin solution.
Use large spoon to scoop off foam from surface of gelatin solution. Dispose of foam in sink while running warm tap water.
Spray gelatin block mold with silicone spray mold release for ease of gelatin block removal. (Ensure gelatin mold is clean and dry. Small particles of dried gelatin solution adhering to internal surfaces of mold can produce gouges in gelatin block when it is removed from the mold.)
Carefully pour gelatin solution into mold.
Let stand at room temperature for 4 hours to hydrate. Tent mold with aluminum foil to protect gelatin from airborne contaminants.
Place filled mold, uncovered, in refrigerator at 39° F.
Wait at least 24 hours before attempting to remove gelatin block from mold.
When removing gelatin block from mold, pour a small amount of ice cold water between mold and gelatin to ease removal. After gelatin block is extracted from mold, blot water from block using paper towels.
Wrap gelatin block in plastic bag. Return to refrigerator at 39° F. After gelatin block is removed from mold, wait at least 24 hours before shooting block to allow gelatin temperature to stabilize.
Gelatin is ready to shoot when 48 hours old. Larger gelatin blocks may require additional time to properly cure before use.
Use ice chest (add no ice) as an insulated container to transport ordnance gelatin to shooting range. Use thermometer inside ice chest to monitor temperature.
Note: A couple of milk containers, filled with water and frozen solid, can be placed into the ice chest to cool the interior. The milk containers should be put inside the ice chest at least couple of hours prior, and removed immediately before placing the gelatin block inside. Do not add any ice to the ice chest after the gelatin block has been placed inside. Doing so will produce temperature variations throughout the gelatin block, and invalidate your test results.
- Remove gelatin block from ice chest, unwrap it, and place it on test stand. Position chronograph sensors (skyscreens/photoelectric screens) directly in front of gelatin block to measure projectile impact velocity.
Note: Time is of essence. Depending on ambient air temperature, the gelatin block will begin to warm as soon as you remove it from the ice chest. It's best to test in an environment in which the ambient air temperature is 65° F or cooler. A good rule of thumb to follow is to complete your testing within 20 minutes after removing the gelatin block from the ice chest. If you believe a gelatin block may have warmed, verify it meets calibration standards.
- Calibrate gelatin block by shooting a steel BB into it at a velocity of 590 feet per second ± 30 fps. The BB should penetrate 8.5 centimeters. (Note: If BB velocity is not exactly 590 fps, refer to Bullet Penetration, Figure 5-2 Velocity Variation Correction to Measured BB Penetration Depth, page 84, to correct for velocity error. Whereas if BB velocity is correct, or velocity error has been corrected, and BB penetration depth does not meet calibration standard [e.g., 9.5cm instead of 8.5cm], refer to Bullet Penetration, 2005 Second Printing, pages 256 - 261, to correct for penetration error.) Record calibration data.
Note: We use a calibration standard of 7.7 - 9.4cm BB penetration (corrected) at 590 fps velocity. This provides a calibration tolerance of plus or minus 10 percent. As long as the BB achieves this range of penetration/corrected penetration, we consider the data to be valid as measured.
If two or more gelatin blocks are going to be lined-up end-to-end to capture the entire wound path of the bullet under test, each and every gelatin block must be calibrated in accordance with step 17.
After calibrating, the gelatin block(s) is ready for terminal ballistics testing. Depending on the cartridge being tested, more than one bullet can be shot into the block(s). Carefully plan each shot to avoid overlap of previous temporary cavities/bullet paths, and to ensure the bullet will not exit the sides or top of the block.
It's best to measure penetration depth after each shot is completed. This practice minimizes loss of data if one bullet collides with another in the gelatin block.
After penetration depth is measured, the bullets can be recovered at a later time to measure expansion diameter using dial caliper.
If denim cloth is used to test bullet expansion performance, cut a 4 feet long, 6 inch wide strip of cloth. Fold the cloth strip lengthwise twice. This produces a cloth test fixture that's 1 foot long and four layers thick. Place the cloth loosely against the gelatin block, half on top of the block, half hanging over the front of the gelatin block.
If shooting at an outdoor range, shade the gelatin block from direct sunlight using a piece of cardboard or similar device.
Figures 1 through 8. Ordnance gelatin
preparation and testing.
(Click on thumbnails to view enlarged photographs)
25-lb. drum of Kind & Knox Type 250A ordnance gelatin powder (minimum quantity that can be purchased from Kind & Knox). Also shown are Ohaus model 750-00 triple beam balance and plastic propeller-type paint mixer that attaches onto electric drill to mix gelatin solution.
A lightweight container is used when weighing ordnance gelatin powder. This container weighs 44-grams. The balance is set-up to weigh 500-grams of gelatin powder plus the weight of the container.
5 gallon plastic bucket is used to mix 10% ordnance gelatin solution, consisting of 9 liters of hot water (130° F ± 10° F) and 1 kilogram of ordnance gelatin powder. The standard kitchen Pyrex measuring cup on the left has a maximum measuring capacity of 1 liter. While it is adequate for measuring the proper proportion of water to the gelatin solution, we discovered that it is easy to lose count of the number of liters of water added. It is better to use a measuring container with greater capacity, such as the plastic 3 liter graduated pitcher on the right. The thermometer shown is adequate for measuring both water temperature and refrigerator temperature.
This gelatin block mold measures 7"H x 6"W x 16" L and is used to cast standard FBI size (6x6x16") gelatin blocks. It is constructed of 16 gauge stainless steel and was manufactured by a local sheet metal shop for approximately $60.00. Also shown is an aerosol can of silicone mold release, which is sprayed onto the internal surfaces of the gelatin mold to prevent the gelatin from adhering to it.
Propionic acid is added to the ordnance gelatin solution to inhibit the growth of microorganisms. We use a 12cc hypodermic syringe to measure 5cc propionic acid per batch of 10% ordnance gelatin solution. A 6-inch length of aquarium air hose is attached to the syringe to make it easier to draw the liquid into the syringe from the bottle
Ordnance gelatin block test stand. The table top of this portable test stand measures 20"W x 36"L, and provides ample work area to handle large blocks of ordnance gelatin. The block shown measures 10"W x 6"H x 18"L and weighs approximately 45 lbs. This test stand was designed to support two 70-lb. gelatin blocks measuring 10"W x 10"H x 18"L, which are placed end to end lengthwise to capture the entire wound tracks of centerfire rifle bullets and shotgun slugs. The three triangular devices are skyscreen photo-sensors used with the Oehler 35P proof chronograph. The Oehler 35P provides greater measurement confidence of projectile velocities than chronographs that use only two skyscreens. The skyscreens are evenly spaced exactly 1-ft. apart. The skyscreen support rod is attached directly to the test stand to minimize set-up time, and ensures the skyscreens are properly aligned with the test stand. When we test, we position the test stand so that the distance between the test gun muzzle and front of the gelatin block is approximately 10-12 feet.
Ordnance gelatin block calibration. A steel BB is shot into the gelatin block at a measured velocity of 590 feet per second. The BB should penetrate 8.5cm ± 0.85cm (7.7cm to 9.4cm) to ensure the results obtained are accurate. We usually shoot our calibration BB into the lower right corner of the gelatin block. We do this for two reasons: 1) it locates the trajectory of the BB very close to the skyscreen photo-sensors, which minimizes errors caused when the skyscreens don't detect the small diameter BB passing overhead, and 2) the BB is conveniently located in the gelatin block were it can be easily seen and measured, plus the BB is out of the paths of the subsequent test bullets. The BB in this block is a little rusty because the block has been stored in the refrigerator several days after shooting. The propionic acid, which is used as a preservative, accelerates oxidation of BBs and bullets alike.
Close-up of gelatin block that is prepared to perform testing with denim cloth. The denim cloth is cut into a 6-inch wide, 4-ft. long strip and folded twice lengthwise to produce four layers. The test cloth is placed on the gelatin block as shown. This photograph was staged in a residential back yard for illustrative purposes only. Please disregard the background.
SOURCES TO OBTAIN EQUIPMENT/MATERIAL FOR ORDNANCE GELATIN TESTING
Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma, by Duncan MacPherson
P.O. Box 772
El Segundo, California 90245
Kind & Knox Type 250A Ordnance Gelatin Powder (Best transparency for photographing gelatin blocks)
(25 lb. drum minimum purchase):
GELITA North America
P.O. Box 927
Sioux City, Iowa 51102
Telephone: (888) 443-5482
Vyse Gelatin Company, Incorporated (Less expensive and less transparent than Kind & Knox gelatin)
Vyse Gelatin Co., Inc.
5010 N. Rose St.
Schiller Park, IL 60176
Telephone: (800) 533-2152 or (847) 678-4780
Triple beam balance (Ohaus model 750-00):
Precision Weighing Balances
10 Peabody Street
Bradford, Massachusetts 01835-7614
Telephone: (978) 521-7095
Graduated pitcher (3000cc High Form Graduated Pitcher, Item No. 46208LK):
Consolidated Plastics Company, Incorporated
8181 Darrow Road
Twinsburg, Ohio 44087-2375
Telephone: (330) 425-3900
Propionic acid (Baker U330-7, 500 ml):
Thomas Scientific (Catalog No. 0148-N40, $28.20)
P.O. Box 99
Swedesboro, New Jersey 08085-0099
Telephone: (800) 345-2100 or (609) 467-2000
Silicone spray mold release (IMS Super 33 Silicone Spray, No. S3312A Super Concentrated Mold Release, 9.25 oz.):
IMS (Injection Molders Supply Company)
10373 Stafford Road
Chagrin Falls, Ohio 44023-5296
Telephone: 1-800-537-5375 or (440) 543-1615
Chronograph (Oehler model 35/3 Proof Chronograph):
Oehler Research, Incorporated
P.O. Box 9135
Austin, Texas 78766
Telephone: (512) 327-6900
Denim cloth (16 ounce test standard):
International Wound Ballistics Association
P.O. Box 701
El Segundo, California 90245
Telephone: (310) 640-6065
We had our gelatin molds custom built for us by a local sheet metal shop. The material used is 16 gauge stainless steel. One mold (6"W x 7"H x 16"L) was built to cast gelatin blocks that meet FBI specifications (6x6x16 inches). This mold cost approximately $60.00. A second mold (10"W x 11"H x 18"L) was built to cast larger blocks. This larger mold can cast gelatin blocks measuring 10x6x18 inches (requires two batches of gelatin solution) and 10x10x18 inches (requiring three batches of gelatin solution). This mold cost approximately $80.00.
One batch of ordnance gelatin solution produces approximately 580 cubic inches of gelatin solution.
A clean and undamaged U.S. Military .50 caliber ammo container can be used as a makeshift gelatin block mold. The ammunition container measures 5¾"W x 7"H x 11"L. One batch of ordnance gelatin solution can produce two gelatin blocks measuring approximately 5¾"W x 4.5"H x 11"L. Two batches of ordnance gelatin can produce three gelatin blocks measuring approximately 5¾"W x 6"H x 11"L.
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