Using store bought gelatin for ballistics testing.

There is an assumption that using store bought gelatin instead of 250A ballistics gel is the same, and people seem to be getting good results when using it.

So, what is gelatin, what is 250A gelatin, and how is it different from the stuff you can buy at the grocery store?

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According to the Knox Gelatin website it is, “A protein substance which yields gelatin and is found in the bones, skin and connective tissue of animals.  In manufacturing, unflavored gelatin is extracted from the collagen by hot water, then concentrated and filtered for purity and clarity.” It is then dried and ground into a powder into the powdered gelatin we know of today.

What is 250A gelatin? The 250 refers to the bloom strength of the gelatin, and it varies depending on its use. The “A” in the name refers to the process used to make it. There is “A” and “B”. “B” is used mostly as an industrial gelatin and not stable for our use.

The biggest and most significant difference between store bought gel like Knox gelatin and the Vyse 250 is the bloom strength. The Vyse has a 250 bloom +- 5% whereas the Knox gelatin has a bloom of 225 +-10. This means the Knox brand will be softer than the Vyse ballistics gel and possibly less consistent.

However, there may be a workaround. There is a formula used in the cooking world to change the bloom strength of gelatin.

 “250 (bloom strength in the recipe) – 225 (bloom strength on hand) ÷ 250 (bloom strength in the recipe) x by 32 (or whatever the amount of gelatin is required in the recipe) = Amount needed to add to the recipe to achieve the right strength.”

If I’m doing my math right, I would need to add 3.2 ounces of the Knox 225 bloom in order to bring it up to 250 bloom. The variation would still be +- 10% so it could end up anywhere from 240 to 260 bloom.

To test this out, I bought two pounds of Knox gel on eBay and an additional 4 ounces from the store, so I could get to the 2.2 pounds necessary. I then mixed it as normal, the same way as mixing the Vyse 250A and made a 6x6x16 inch gel block.

Visually the two gel powders look a little different, with the Knox brand lighter in color and smaller grain size. The finished block was also lighter and clearer.

Knox on the left and Vyse on the right
Knox on the left and Vyse on the right

One issue I ran into was how foamy it was. My normal way of mixing it to use a paint mixer on a cordless drill. This has a tendency to introduce some amount of foam in the mix. I don’t usually worry too much about it because the foam dissipates after a few minutes. Not the case with the Knox. It took a long time before I could get all in the mold and then there was a foam layer on top that I had to peel away. It had the consistency of meringue. After about two hours I scraped off the foam and noticed there appeared to be a usable block of gel. After a few days in the fridge, I removed the gel from the mold and shot it with the BB gun to see how well it calibrated. I shot one BB in the gel, and it penetrated to 3.75 inches.

Top Knox gel Bottom Vyse after poring

After sitting for two hours and removing the foam

My intentions was to test this block side by side with the Vyse block using the Speer .38 Spl Gold Dot test I posted a few days ago. This block stayed in the cooler with a thermometer while I shot the Vyse block. Right after finishing the test on the Vyse block I swapped them and repeated the test.


The first round had a 841fps and penetrated to 12.25 inches. The recovered expansion was .57 by .54 inches and the recovered weight was 135.8 grains.

Round two’s velocity was 877fps and it penetrated to 12.5 inches. Expansion was .56 by .55 inches and the recovered weight was 135.5 grains.

My chronograph was giving me fits and I did not get any velocity readings with the clothing test.

The first round through the clothing covered block traveled 13.25 inches. It expanded to .57 by .55 inches and the recovered weight was 133.6 grains.

The last round in the test penetrated to 12.75 inches and also expanded to .57 by .55 inches The recovered weight was 135 grains.

The average penetration for all four shots was 12.69 inches and was just about what expiated. However, it was slightly less than the Vyse 250A block that was shot, but why? The BB calibration on this block was 3.75 inches. On the Vyse gel block it was 4 inches and it had an average penetration of the four rounds was 14 inches, about an inch and a half more. And the clear gel block came in-between at 13.5 inches.

Volume two number two of the IWBA has a mathematical formula or correcting out of spec gel blocks. At some point I will have to get my head around the math and figure it out. But for now, I think it shows the importance of properly calibrating the block.

So, closing thoughts. Yes, using store bought gelatin is a very viable alternative for testing your own ammo. If you prepare it properly and it calibrates and you control the temperature at testing, then I see no reason why you can’t get good results. You can also do it at a reasonable cost if you shop around. There are several websites and YouTube videos on making your own and all seem to do it a little differently. I encourage everyone who is interested to give it a try and see how your ammo will do.

Please feel free to leave a comment and tell me what you think.


  1. Thank you for sharing this information. Some of us do test our own bullets at home. Knox is good stuff and easy to find. My son tested airgun pellets years ago for a science project using uncalibrated Knox. It was fun and intriguing!


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