Wet Pack Tissue Simulant Preparation

This information is excerpted from the article "Water Soaked Newspapers: An Alternative for 10% Ordnance Gelatin," by George Bredsten, in Volume 3, No. 1, of Wound Ballistics Review.

For those who are unable to use 10% ordnance gelatin, but who still are interested in conducting meaningful experiments, there is available a less sophisticated and less expensive alternative tissue simulant.  This alternative tissue simulant is generally called wet pack and is usually described as being water soaked cardboard, magazines or newspapers.

There has been and continues to be some criticism that wet pack results are neither consistent with actual bullet wounds nor are the results replicable.  Some persons, who have tested their versions of wet pack, claimed bullet performance characteristics of a given load varied significantly from test to test.  Such varied results can most likely be attributed to a haphazard preparation and/or use of wet pack.

An early reference to wet pack merely mentioned the material used was a wet telephone book'. A much later reference provided a somewhat more detailed description, i.e., thin sheets of water soaked cardboard.  Instructions detailing the protocol for the preparation, calibration and use of wet pack were conspicuous by their absence.  

This protocol  presents wet pack preparation based on the measured and recorded performance characteristics of bullets used to take dozens of big game animals.  Also, the observed big game animals' physical reactions to the affect of bullet penetration were recorded. The type and extent of an animal's reaction to bullet impact and penetration prove helpful in assessing the general effectiveness of a particular type bullet wound.

If the results of wet pack are to provide meaningful data, it is essential that such tests be replicable and that the test results provide data which are relevant. Replicable tests permit interested persons to conduct tests, the results of which may either support or dispute the reported data.  However, in order to correctly replicate tests, the test medium must first be calibrated.  This makes it possible to compare "apples with apples" and not "apples with oranges."  To provide for consistency, relevancy and pragmatic values, a protocol for the preparation, calibration and use of wet pack is given here.

Ballistic Wet Pack Preparation

  1. Use standard size newspapers (folded in half, about 11.5" by 13.5"), with all "slick" type papers removed.

  2. Immerse newspapers into an appropriate size water filled container; e.g., 55-gallon drum or water tank.

  3. Before being soaked, there are approximately 1730 pages in a six inch thick stack of newspapers. The volume of this six inch thick stack of newspapers is about 932 cubic inches.

  4. Place sufficient weight upon the newspapers to keep them submerged.

  5. Newspapers are to remain submerged until the newspapers are water saturated.

  6. Remove about one to perhaps two inches of saturated newspapers and place on a smooth, flat surface. The folded edges of the newspapers to be in alternate positions; i.e., top, bottom, top, etc.

  7. Using a rectangular press (the size of the folded newspapers) apply pressure to the saturated news­papers to remove excess water and eliminate possible internal voids.

  8. Continue this process (steps 6 and 7) until a stack of pressed newspapers (that was six inches thick when dry) weighs 40 pounds.

  9. When a six inch thick stack of wet pack weighs forty pounds, a slight pressure with the pad of an index forger results in small beads of water forming on the surface of the wet pack.

  10. A given thickness of wet pack is prepared for each test and then placed on a wet pack frame. Regardless of the actual thickness, the total weight of the prepared wet pack must have a ratio of six inches to 40 pounds. For example, a 12 inch thick stack would weigh 80 pounds and a 30 inch thick stack would weigh 200 pounds.

  11. For convenience, the folded newspapers may be cut into a smaller size; e.g., when cut in half the required six inch thick stack weight would be 20 pounds. The calculated volume of this smaller size six inch stack of newspapers would be about 466 cubic inches.

  12. A rectangular board the size of the folded newspapers of 3/4" thick plywood is placed at the rear of the wet pack to provide vertical support for the wet pack.

Ballistic Wet Pack Calibration

  1. Calibration is to be undertaken within two hours of preparation and in all situations within five minutes before conducting expansion/penetration tests of the ammunition under consideration.

  2. A .357" diameter, 148 grain wadcutter, lead bullet is given an instrumental velocity of 700±15 feet per second at 10 feet (note that this lead should be "pure" and not a harder alloy).

  3. If handloading is not done, the Remington, 148 gr "pure" lead wadcutter commercial target load (Index: R38S) may be used as its velocity from a four inch barrel revolver is usually within the acceptable limit for velocity variations.

  4. The bullet is to impact the wet pack at 15 feet in the lower left quadrant.

  5. The bullet is to impact about three inches in from the left side and three inches up from the bottom.

  6. The acceptable parameter for bullet penetration is 6˝ ± 5/16 inches. Note that this "pure" lead bullet should not show any expansion or rounding of the sharp shoulders.

Ballistic Wet Pack Testing

  1. After the calibration standard is met, a wet pack test may be conducted at the distance or distances of interest.

  2. The wet pack is to be shaded from direct sunlight and used within two hours of preparation.

  3. The total thickness of the wet pack may vary from test to test; however, bullet performance characteristics comparisons are valid only when the thickness of the wet pack is the same from test to test.

  4. There cannot be any visible affect of one bullet's penetration trajectory upon any other bullet's penetration trajectory.

  5. After the test shots (bullets) have been fired into the wet pack, measurements of the bullet performance characteristics are taken.

  6. There are several methods that could be used to measure bullet performance characteristics, however, only one is given in this protocol.

  7. This method involves separation of the wet pack at given distance intervals and then the horizontal and vertical measurements of the void are measured and recorded.

  8. These measurements are normally taken at intervals of either one or two inches, but can be taken at intervals as small as 1/2 inch.

  9. The total bullet penetration is recorded at the forward most point of the bullet. If the bullet fragments into two or more pieces, the most forward point of each visible fragment is recorded.

Note from Fr. Frog:  I have inserted a single sheet of thoroughly wetted colored paper every inch as a aid in measuring penetration.

Another Calibratable Alternative

Another option for testing bullets at between 700 and 3,000 f/s is to use stacked 1/2 gallon cardboard milk cartons filled with water and stacked snuggly together in a row.  Repeated testing has shown that penetration of bullets in this test media is 1.5 times greater than the same bullet in 10 percent gelatin.  (Bullet penetration in just water (no cartons) is about 1.8 times that of gelatin.)

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As far as I know all the information presented above is correct and I have attempted to insure that it is. However, I am not responsible for any errors, omissions, or damages resulting from the use or misuse of this information, nor for you doing something stupid with it. (Don't you hate these disclaimers? So do I, but there are people out there who refuse to be responsible for their own actions and who will sue anybody to make a buck.)

Updated 2006-06-05