Homemade ballistic gelatin testing

[chopinbloc]

I had this posted in the reloading section but a lot of this is about factory ammo so maybe it belongs here.

Proper ballistic gelatin is made from 250 bloom photographer's gelatin. Problem is, that stuff is fairly expensive. According to Vyse, the gelatin they use is 250 +/- 5, whereas food gelatin is typically 250 +/- 10. There are also variations in other metrics, which you can read about at the link. While these variations may invalidate tests for a ballistics lab, I feel that the results should be close enough as to be useful for the layman to get a general idea of how certain loads perform, especially with cartridges such as the 10mm where there just isn't hardly any good, professional data available. At the very least, the data collected should be far more relevant than water or wet pack and probably more accurate than Simtest or Cleargel. I have verified this by shooting my gelatin with a factory Speer Gold Dot 180 gr .40 S&W and a 75 gr PPU BTHP. In the former case, the result was practically identical to a published FBI test and in the latter case, the results were nearly identical to Molon's (from AR15.com and M4carbine.net) test of the same cartridge. I used grocery store gelatin and had to do some fiddling to get the mix right but was eventually able to get consistent calibration results. Proper calibration is a .177 BB fired at 590 fps +/- 15 fps into a 40 degree block of gelatin. Penetration should fall between 2.95" and 3.75". I initially had some trouble getting the right velocity out of my BB gun but I think I've got it figured out now. Here are some of my tests. Penetration, expansion, retained weight, etc. values are in the descriptions for each video.

Per request, here is my recipe and procedure:

I use grocery store unflavored gelatin in a ratio of 45 cups of hot water to 48 oz of gelatin, which yields about 2.5 gallons of the mixture. I've since made another batch for a total of about five gallons. The cost is about $6.50 for an 8 oz box of gelatin.

I start by measuring out 45 cups of hot tap water and adding a few drops of bleach (to prevent mold), jet dry (to prevent foaming), and cinnamon oil (to clarify). I then slowly add the gelatin while running the mixer. It's easier to just open all the packets first into a bowl. I try to avoid chunks but I think some are inevitable. Once it's all mixed, it goes into the fridge for about a day. This is necessary to give time for the gelatin to fully hydrate. Then I heat it in a double boiler (actually just a two gallon bucket in a large pot) on the stove to remelt it, stir it well with a long spoon and pour into molds. Then it goes into the refrigerator at 39 degrees F. It needs to refrigerate for at least 3 days to fully cool on the inside. It will need to be calibrated immediately before shooting but you may also want to test it at home to be sure your mix is right before heading out to the range.

Proper calibration is a .177 cal BB at 590 fps +/- 15 fps and the penetration should be between 2.95" and 3.75". If you make multiple blocks, they must each be calibrated.

If anyone knows how to embed here, please let me know. Thanks.




10 mm Precision cartridge 180 gr Golden Saber:

http://www.youtube.com/watch?v=RiuvCMsPLGE

10 mm 165 gr Hornady Critical Defense:

http://www.youtube.com/watch?v=sTndHTYkXCc

.22lr CCI Minimag:

http://www.youtube.com/watch?v=ISRj9Zb-pzY

10mm Underwood 155 gr Gold Dot at 1,148 fps:

http://www.youtube.com/watch?v=YRkKoe3g9lA

10mm 200 gr XTP over 8.3 gr of 800-X @ 1,140 fps:

http://www.youtube.com/watch?v=mEqEC8mZLg0

5.56mm 65gr Sierra Game King over 24.0gr of TAC:

http://www.youtube.com/watch?v=0PtAG_6NQOQ

.223 Rem Prvi Partisan 75 gr BTHP:

http://www.youtube.com/watch?v=iTB0sfKF3ec

 

[chopinbloc]

10mm CORBON 180 gr BCSP:

http://www.youtube.com/watch?v=3wEAPXNAkxY

10mm 180 gr Gold Dot @ 1,317 fps:

http://www.youtube.com/watch?v=RuGFfgZb5a0

10mm 200 gr XTP @ 1,037 fps:

http://www.youtube.com/watch?v=jc3_TaAldVo

10mm Buffalo Bore 180 gr Montana Gold bullet:

http://www.youtube.com/watch?v=a_m1hgY5-sc

10mm 200 gr XTP @ 1,142 fps:

http://www.youtube.com/watch?v=EPs2EsdmQS0

7.62x39mm fragmentation from steel plate:

http://www.youtube.com/watch?v=LNoKHNHuWQk




.40 S&W Speer 180 gr Gold Dot (factory):

http://www.youtube.com/watch?v=gVccgbXxMcs

10mm 165 gr Gold Dot @ 1,610 fps:

http://www.youtube.com/watch?v=FR14jBsZpWk

10mm 180 gr XTP @ 1,290 fps:

http://www.youtube.com/watch?v=XahzIeDo1Vk

 

[Skribs]

This is awesome. I will favorite this when I get home, so when I have access to my own private range I can do this for myself.

 

[armedandsafe]

Back in the early '50s, Dad did some of that. We weren't too interested in the comparison of our mix to that used in crime and test labs, but did mix it fairly heavily, compared to the recipe on the box. We poured it into gallon milk jugs (cardboard, on those days) and stuck a bone down into it. We were interested in the comparative reaction of various bullets were were contemplating on reloading for the 30-06s. We shot them at 250 yards to keep from totally destroying the jugs on impact.

We settled on the Sierra 180 grain boat tail soft point.

Pops

 

[chopinbloc]

We were interested in the comparative reaction of various bullets...

Frankly, this is the only thing that ballistic gelatin is good for, anyway. No matter how it's mixed, gelatin can't predict what will happen when a bullet strikes tissue except in a very general sense. For that matter, tissue cannot predict what will happen when a bullet strikes tissue. What properly calibrated gelatin can do is provide a level field on which to compare various bullets to each other.


Sierra makes GREAT bullets.

 

[mgkdrgn]

Very nice, very very nice indeed! Good Job!

May I have a box of Gold Dots please!

 

[coloradokevin]

Thanks for your detailed post, Chopinbloc! I've been looking for an affordable home ballistic gelatin recipe

 

[JTHunter]

Impressive testing Chopinbloc.
From these results, it appears that the Remington Golden Sabers and the Speer Gold Dots do a better job at mushrooming and they have more "cutting edges" than the Hornady XTPs.

 

[Trent]

Woah, tagged for when I'm not working and can read it all.

 

[Trent]

Looks pretty good for the Gold dots and golden saber projectiles.. what I keep in the 9mm and 45, respectively.

I used to load a bunch of XTP's but Golden Sabers got a lot cheaper. Always wondered if that was a good decision, guess it was.

 

[Dave P]

Great data!

 

[Ranb]

What do you do with the blocks of gelatin that were shot? Can you re-melt and pour back into molds for re-use?

Ranb

 

[chopinbloc]

Yessir. I just melt them down, pour them through a strainer and then a wire mesh coffee filter to remove the bits of denim and bullet fragments, then back into a mold for the next test. After two or three tests, enough water has evaporated to drive the calibration figure down so I add a cup or two of water. I'm sure eventually it will get cloudy enough that I'll need to make a new batch.

 

[Skribs]

What are you using for a mold?

It's occuring to me that if I did this at home, I'd need more fridge space and probably some more cooking utinsils. And some skill in cooking...and some restraint in not eating the jello.

 

[chopinbloc]

LOL. It wouldn't taste very good at all. Especially with the bleach and Jet Dry. The cinnamon oil smells nice, though.

I just use cheap Sterlite plastic bins I bought at Walmart. You can work backwards by measuring how much fridge space you're willing to use (I use the bottom shelf in my garage fridge), then finding the molds that would fit, then doing the math on how much volume you can make.

 

[Skribs]

The cinnamon oil smells nice, though.

I'm anosmic. I can't smell.

 

[chopinbloc]

No wonder you'd be willing to eat that stuff. ;^) Ugh.

 

[Shawn Dodson]

Frankly, this is the only thing that ballistic gelatin is good for, anyway. No matter how it's mixed, gelatin can't predict what will happen when a bullet strikes tissue except in a very general sense. For that matter, tissue cannot predict what will happen when a bullet strikes tissue. What properly calibrated gelatin can do is provide a level field on which to compare various bullets to each other.

The test of the wound profiles’ validity is how accurately they portray the projectile-tissue interaction observed in shots that penetrate the human body. Since most shots in the human body traverse various tissues, we would expect the wound profiles to vary somewhat, depending on the tissues traversed. However, the only radical departure has been found to occur when the projectile strikes bone: this predictably deforms the bullet more than soft tissue, reducing its overall penetration depth, and sometimes altering the angle of the projectile’s course. Shots traversing only soft tissues in humans have shown damage patterns of remarkably close approximation to the wound profiles.

The bullet penetration depth comparison, as well as the similarity in bullet deformation and yaw patterns, between human soft tissue and 10% ordnance gelatin have proven to be consistent and reliable. Every time there appeared to be an inconsistency…a good reason was found and when the exact circumstances were matched, the results matched. The cases reported here comprise but a small fraction of the documented comparisons which have established 10% ordnance gelatin as a valid tissue simulant.

--“The Wound Profile & The Human Body: Damage Pattern Correlation.” (Martin L Fackler, MD, Wound Ballistics Review, 1(4): 1994; 12-19)

 

[chopinbloc]

That sounds eerily familiar. ;^)


Let me clarify: I'm not saying that ballistic gelatin results are without merit. I'm just saying that the interaction of a projectile and tissues often involve many variables that are difficult to reproduce or control for. Ballistic gelatin is the industry standard tissue simulant and it is perfectly adequate for the intended task. Other mediums may perform well but I am unaware of any testing that indicates whether the results from the other mediums are analogous to 10% ordnance gelatin.

My results shouldn't be taken as gospel, either. While I am personally confident that my gelatin yields results that are fairly consistent with the results from professional labs, the fact is that my gelatin is not 250A bloom and my preparation procedure varies slightly from what the pros do.

 

[Shawn Dodson]

That sounds eerily familiar. ;^)

It sure does, doesn't it? lol

I'm just saying that the interaction of a projectile and tissues often involve many variables that are difficult to reproduce or control for.

This is a common misconception that Duncan MacPherson also address some years ago:

When a bullet is penetrating any material (tissue, water, air, wood, etc.), the total force the bullet exerts on the material is the same as the total force the material exerts on the bullet (this is Newton’s Third Law of Motion). These forces may be represented as a combination of shear forces and inertial forces (don’t be concerned if these words sound too technical – the concepts are easy). Shear force may be thought of as the force that resists deformation; if you push on a wall you are creating shear forces in the wall material that resist your push. If you push your hand down very slowly on a water surface, you feel no resisting force; this is true because a liquid cannot support a shear force….

You can fan your hand back and forth in air quite rapidly because there seems to be no resistance, but a similar fanning motion cannot be done nearly as rapidly underwater because moving the water can take all the strength you can muster. The forces that resist the movement of your hand in water are inertial forces….

A bullet penetrating a soft solid (tissue or a tissue simulant like gelatin) meets resistance that is a combination of shear forces and inertial forces….

…Anyone who has worked with gelatin knows that a finger can be pushed into gelatin with a force of only a few pounds; this force is similar to the resistance to a finger poked into the stomach, but the tissue does not fracture as easily as gelatin does. A finger poked into water does not meet this kind of resistance, which is due to shear forces. Penetration of a 9mm bullet at 1000 ft/sec is resisted by an inertial force of about 800 pounds; it is obvious that the presence or absence of a 3 to 5 pound shear force makes no practical difference in the penetration at this velocity. This also explains why the fact that gelatin fractures more easily than tissue does is not important.

The extension of these dynamics to soft tissue variation is obvious. Different types of tissue present different resistance to finger probing by a surgeon, but the surgeon is not probing at 1000 ft/sec. Different tissue types do have differences in the amount of shear force they will support, but all of these forces are so small relative to inertial forces that there is no practical difference. The tissue types are closer to one another than they are to water, and bullet expansion in water and tissue are nearly identical at velocities over 600 ft/sec where all bullet expansion takes place (See Bullet Penetration for a detailed explanation of bullet expansion dynamics).

Since inertial forces depend on accelerating mass, it makes sense that these forces should be lower at lower velocities (because the penetrated material cannot be accelerated to a velocity higher than the bullet). Shear forces have little velocity dependence, and as a result, shear forces are a much larger fraction of the total when bullet velocity is below the cavitation threshold. This low velocity effect is the reason that total bullet penetration depth is much different in water and in tissue or a valid tissue simulant.

As a result of the penetration dynamics, most soft solids with a density very near soft tissues (i.e., near the density of water) are satisfactory tissue simulants when shear forces are not important. However, total penetration depth depends significantly on dynamics at velocities below 400 ft/sec, so most materials do not properly simulate penetration depth. The total bullet penetration depth in tissue and a valid tissue simulant should be the same; standard practice is to use calibrated gelatin to insure this. In effect, gelatin calibration is done to ensure that the shear forces in the gelatin are the same as in typical soft tissue (as described in Bullet Penetration, the technical parameter used in the dynamic is viscosity).

-- “Wound Ballistics Misconceptions.” (Duncan MacPherson, Wound Ballistics Review, 2(3): 1996; 42-43)

Other mediums may perform well but I am unaware of any testing that indicates whether the results from the other mediums are analogous to 10% ordnance gelatin.

None of these other mediums have been validated against soft tissues or a valid soft tissue simulant. The temporary and permanent disruption produced in these other mediums have not been correlated to the same disruption produced in soft tissues or a valid soft tissue simulant.

 

[Ranb]

Does this stuff look like it would work?

http://www.amazon.com/Now-Foods-Gel...=1354665106&sr=8-3&keywords=knox+gelatin+bulk

Ranb

 

[Skribs]

What do you store it in during the first day in the fridge?

You also mentioned 2.5 gallons of mixture and a 2 gallon bucket; do you do the second mixing in chunks?

 

[Shawn Dodson]

A SIMPLIFIED 10% ORDNANCE GELATIN PREPARATION AND TEST PROCEDURE - http://www.firearmstactical.com/tacticalbriefs/volume3/number2/article1.htm

A Method for Recycling Ordnance Gelatin - http://www.firearmstactical.com/pdf/ordgel_recycle_procedure.pdf

(Be careful not to heat the gelatin solution above 130-degrees Farenheit.)

 

[Reloadron]

Really a nice job well done with great images. Thanks for sharing the data and for the time and effort you put into this.

Ron

 

[chopinbloc]

That Amazon link would probably work great and a lot cheaper than I paid. I paid about $40 for 3 lbs. You'll obviously need to adjust the water amount accordingly and it might be a good idea to start low on the water and add as necessary to get to the right calibration.

I just poured it into molds for the first day. After that first time mixing it, it only needs to be remelted and poured into molds after each use. That first day is just to get it well hydrated.

Yes, a double boiler and a thermometer is strongly advised. The mixture is a very viscous liquid at room temperature so you really don't need to get it very warm to melt and reform it.