Wednesday, June 22, 2022

DIY Ballistic Gelatin

One of the most important pieces of information to know about ammunition performance, whether for hunting or self-defense, is how it actually behaves when used.

There have been many different bullet testing systems used over the years, including live animals. For those with a morbid fascination, read up on the 1904 Thompson–LaGarde Tests. For any listeners with a more delicate constitution, avoid articles with pictures.

Back in the mists of time I would use a copy paper box full of phone books (kids, ask your parents) in order to test bullet penetration and expansion. If I was being really thorough, I would test twice, once with dry phone books and once after soaking them with water. The difference between wet and dry paper can produce some interesting changes in expansion of soft point and hollow point bullets. 

My phone book tests were certainly not scientific, but they did give me a relatively consistent medium to compare projectile behavior. Since phone books are pretty much a thing of the past now, other options need to be explored. Modeler’s clay has been used for this purpose with some success; it shows primary expansion and penetration fairly well. However, like the phone books, it’s really only comparable to other blocks of clay. The same can be said about water jugs, cinder blocks, and even peeps.

Ballistic gelatin is currently the industry standard for testing bullet performance. It can be purchased ready to use, or mixed up as needed. It can even be melted down, recast, and reused. It can even be made at home from scratch, considerably reducing the price, although the end result will generally be less consistent than the purchased type. 

The standard ballistic gelatin block is called 10% gelatin because the mixture is 10% gelatin to 90% water. There are also 20% ballistic gelatin blocks, but they are less frequently used and considerably more expensive. In order to make a 10% ballistic gelatin block at home, certain supplies and resources will be necessary.

  • An appropriate mold, preferably something smooth-sided and slightly wider at the opening for ease of removal.
  • Non-stick spray for coating the inside of the mold.
  • Unflavored gelatin (Knox brand is recommended).
  • Water.
  • A stirrer, such as a wooden spoon.
  • Measuring cups and spoons.
  • Enough space in a refrigerator for the mold(s).
This process requires a mixture of approximately 7 ounces of gelatin per 2 quarts of water for a roughly 10% ballistic gelatin product. The gelatin to water ratio may need to be adjusted slightly depending on consistency.
  1. While the gelatin powder and water can be combined right in the mold, I’ve read it works better if blended in a separate container. Use warm water and make sure the gelatin powder is fully dissolved.
  2. Once it’s prepared, spray the inside of the mold with a light coating of non-stick spray and pour the gelatin mix into the prepared container. 
  3. Place the mold in a level position in the refrigerator and let sit until fully hardened. This will take between 8 and 12 hours. Don’t harden the mix in a freezer, or the resulting block will be cloudy and possibly prone to splitting.
  4. After it’s fully hardened, keep the ballistic gelatin cool until ready to shoot.
For deeper penetrating bullets, several blocks can be laid end to end. Make sure to take pictures and record the results; after all, as said by ballistics expert Alex Jason and recounted by Adam Savage, “The only difference between screwing around and science is writing it down.”

Post shooting care is fairly simple: brush off any lose debris, extract any bullet fragments, and (if still relatively intact) use again. According to several sources, trying to filter any bits and pieces out of the gelatin can be challenging unless it’s heated to a more liquid state. If trying this, be careful not to over-heat or the gelatin may not fully harden again, then pour it back into the mold for another trip to the refrigerator. If prepared properly and maintained correctly, home-made ballistic gelatin can be reused a number of times before it’s no longer useful as a test medium.

I recently picked up some Kroger’s brand unflavored gelatin on sale and I will be experimenting with making up a batch of ballistic gelatin myself in the next few weeks. I’ll write up how that worked in a future post.

Remember, measure twice and cut (with water) once. Good luck and safe shooting.

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