HANDY! Milk Jug to Ballistic Gel Conversion Formula

[Bigslug]

Came across this online on a YT vid titled "Lock & Load with **** Fairburn" - claims to have been involved with Fackler back in the early days of what has become modern wound ballistic science. https://www.youtube.com/watch?v=pDdEBesIxJ8&t=29s

Since actual pig-based ballistic gelatin is expensive, heavy, bulky, and in other ways complicated to work with, he wanted a decent way to convert results obtained from shooting a row of common gallon milk jugs filled with water. Seems like better science than my rough estimates have come up with.

Final numbers are determined by inspecting the extent of damage caused to the final jug that the bullet comes to rest in and applying a modifier.

Each of the jugs penetrated before the final one gets a penetration value of 6".

If the final jug is penetrated on the front wall, with no damage to the back, add 3"

If the back wall is dented, add 6"

If the back wall is cracked, add 6.75"

If it dents the leading wall of the next jug, add 7.5"

If the leading wall of the next jug is broken, add 8"

Conversion factor: add the variables up and divide by 1.55 for handguns or 1.3 for rifles with velocities over 1800 fps. The result will be your rough equivalent gelatin penetration number.

Basically, if you're comparing to the FBI's "ideal" penetration range of 12-18" in gel, you start making minimum at damaging the boundary layers between jug #3 and #4, and you make the 18" maximum between entering and denting the back wall of #5.

I haven't wrung this out against a known-quantity duty round yet, but it does seem to jive with the 3-5 jugs most duty rounds seem to give.

Have fun kids! Stay dry!

[GrapeApe]

Cool, thanks Big

[CPJ 2.0]

For less than $20 you can whip
Up your own gel block. I’ve been pondering do that.

[Bigslug]

For less than $20 you can whip
Up your own gel block. I’ve been pondering do that.

At the point you allow for the means to mix, making the mold, the fridge space to put the mold in, transporting to the range cold, un-molding, chronographing and checking gel density against a BB gun. . .applying some math to a stack of milk jugs begins to look really appealing. I've assisted ammo reps during a number of their demo shoots - the "official" process is fascinating and fun, but a real pain in the ass.

I've got plenty of "bare gel" data on Winchester SXT in 9mm, .40, and .45 - I should be able to start testing it against Fairburn's jug formula fairly soon. I'm pretty excited about using the modifiers to account for the boundary layers of plastic and divide up that last jug penetration into measurable fractions. I'm no statistics wizard, but it looks to me like this formula will keep the margin of error to within a 2" window of the actual gel result. If that holds, use of milk jugs goes from screwin' around to something bordering on actual science.

SCIENCE!.jpg (137.25 KiB) Viewed 626 times

[CPJ 2.0]

And at the end of the day…..gel or jugs….it really doesn’t mean poop in the grand scheme of things.
Effect on the intended target does.

[Bigslug]

And at the end of the day…..gel or jugs….it really doesn’t mean poop in the grand scheme of things.
Effect on the intended target does.

Well, I'm 100% in favor of sentencing convicted felons to ballistics testing labs, but since that seems to be generally frowned upon, the grand scheme requires us to use something else. Cleanup is easier with jugs anyway.

In all seriousness, water has the real advantage of being the most reliably consistent media we can use, and as long as you don't deviate into the thicker "milk jugs" used for pool chlorine, the plastic thickness is going to be very consistent as well. If this guy's math tracks with the labor- and conditions-intensive Jell-O results, we can roll with jugs with something more reliable than redneck guesswork.

My two most handy bare gel test figures for 9x19 147 grain SXT are averaging right around 15". That SHOULD put it into jug #5 with maybe / maybe not denting of the back wall. I ought to be able to orchestrate a "kill" or two in the next couple weeks to see if this bears out. Stay tuned!

[CPJ 2.0]

All test media still only tells us how a bullet performs in test media. At the distance said media is from the muzzle.
I’ve seen a .308 130 grain Speer varmint bullet with a MV of 2000-ish FPS go through a deer at 100 yards,(1714 estimated impact velocity) same bullet leave a gaping flesh wound and not exit in a feral cat at 15 yards.
What’s that equate to in jug or jell? Or jugs of gel? Or big jugs of a crack whore who’s trying to shank you for your wallet?
Doesn’t really matter. Jugs and gel don’t have hair, skin, bones or voids like critters do.

I get it, it’s sciency….but in the grand scheme I don’t think it makes no Nevermind.

[GrapeApe]

I agee, to a point.
Gel, water, soaked paper all give us a base to compare bullets. I don't buy into it's got to go this deep in gel to be good or that whatever medium replicates tissue, however, I feel it can show you that "this" bullet penetrates/expands better/worse than "that" bullet in the same medium

edited to add: Since there are so many different densities of tissue in a living thing, I actually prefer bullets that some folks would say "over expand" in a consistent medium. Just in a human chest, you have a heart, lungs, liver and bones Not to mention the skin, and varying thicknesses of muscle and fat. All of which have differing densities and behave differently under pressure.

How many of us have recovered a bullet under the offside skin of a deer? I have twice. Both times there were nice holes through the chest wall, but the bullet couldn't punch through the skin

[Zee]

I’m with Grape and Chris on this. I don’t have the time or inclination to deal with gelatin or wet news print. I use jugs and water because it’s cheap and easy. It’s not the perfect medium. But as stated, it tells me how this compared to that. And gives me a repeatable measure of what a bullet will do in perfect conditions. If it can’t perform in perfect, it won’t perform in life.
Now, that’s for handgun bullets. Rifle bullets……….well…….i have a target rich environment and nothing tells the truth like flesh and bone. Gotta love Texas.

[GrapeApe]

....and nothing tells the truth like flesh and bone....

100% agree

[Bigslug]

I use jugs and water because it’s cheap and easy. It’s not the perfect medium. But as stated, it tells me how this compared to that. And gives me a repeatable measure of what a bullet will do in perfect conditions. If it can’t perform in perfect, it won’t perform in life.

DING!!!

Gel is a ruler that lab geeks can use to measure in centimeters. Jugs are a ruler that rednecks can use to measure in inches. What this formula hopefully is is accurate conversion software to bridge the two.

[Japhy]

Anyone ever tried Otey liqilock?
Plumbers use it to gel water when replacing toilets and water heaters.

[CPJ 2.0]

Anyone ever tried Otey liqilock?
Plumbers use it to gel water when replacing toilets and water heaters.

Just googled it, it wouldn’t be any advantage. If it flushes away with water after the repair, it ain’t thicc like our local news anchor.

[Bigslug]

Expanded RA9T.jpeg (43.13 KiB) Viewed 345 times

OK. . .the math on this formula seems to work so far.

I popped two rows of jugs with Winchester RA9T 147 grainers today

One put a dent in the back of the fourth jug (formula value of 24") and the other cracked the back wall of the fourth jug (formula value of 24.75")

Average of those two is 24.375". Divide by 1.55 and that gives a gel equivalency of 15.72". Within an inch of the actual gel measurements, so. . .neat!