Talk:Ballistic gelatin

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[edit] Contradiction?

If ballistic gelatin is calibrated by verifying that a BB shot at normal BB gun speeds penetrates 8.5 cm into the gel, noting that a BB shot at a human normally doesn't even pierce the skin, how can ballistics gelatin be said to "closely simulates the density, viscosity and electrical resistance of human and animal muscle tissue" as claimed in the article? We at least need a source on this. --- Bitt 22:12, 16 April 2006 (UTC)

The gelatin simulates tissue (mainly muscle), not skin; skin is quite a bit tougher due to its greater elasticity, but bullets at reasonable ranges will penetrate it without a problem. Also, a BB at ~600 fps will penetrate skin; it requires a mulit-pump pneumatic BB gun to do that, the spring-air Daisy pump BB guns run about 240-280 fps according to the Daisy website (looking at the "Buck", "Red Ryder", and 499 models). That's about 1/2 the penetration potential (roughly proportional to mass times velocity divided by frontal surface areal) and 1/4 the energy (one half mass times velocity squared). I'll see if I can find some FBI stuff on the density and viscocity--that's what ballisticians are concerned with--the only source I've seen for the "electrical resistance" claim is a MythBusters episode involving urinating on an electrified subway rail. scot 00:07, 17 April 2006 (UTC)

OK, I've found a reputable looking source (the paper from Penn State) that states:

"Although gelatin can simulate the density and viscosity of living human tissue, it lacks the structure of tissue."

From section 1, page 1

And I think the issue you have with BB penetration is covered by both the statement above (skin has structure), and the significant difference between the BB guns used by young idiots^H^H^H^H^H^Hboys to shoot at each other and the BB guns used for ballistic gelatin calibration. I'm going to remove the tag, if you have any other issues post them here and I'll see them. scot 01:22, 17 April 2006 (UTC)

That all seems fair. I'm going to edit that article to include some of this information, since it's somewhat less than obvious. I think I'll remove the "electrical properties" clause, too. I was always irritated by the MythBusters' claim of electrical similarity without any support of it. — Bitt 20:36, 17 April 2006 (UTC)

in his book "bullet penetration , modeling the dynamics and incapacitation resulting from wound trauma " by duncan McPherson, ballistic gelatin is also calibrated by shooting BB pellets at 590 Fps resultin in a penetration of about 8.5 cm. In the same test series he also shoots the leg of a freshly killed pig (including skin) with the same projectile and speed which results in a penetration of about 8.8 cm. showing that a BB pellet is more than capable of penetrating human-like skin and tissue.(edit 29 august 2006)

Right, but 590 fps is the speed of a BB from a pneumatic air rifle, not the speed from a typical BB gun, which runs about 250 fps for a spring air Daisy, or about 400 fps for a CO₂ BB pistol; a steel BB shot from a magnum 12 gauge will penetrate even further. Penetration is primarily a function of momentum, so tripling the velocity of the Daisy BB gun will give you about 3x the penetration. Skin, unless stretched very tight or backed by bone, will take the 3 cm of displacement without tearing. scot 01:50, 30 August 2006 (UTC)

[edit] Electrical similarity

Can anyone support the claim of electrical similarity besides the various MythBusters episodes, which themselves seem unsupported? — Bitt 20:38, 17 April 2006 (UTC)

Actually, the "research" in this case may have been as simple as them sticking an ohmmeter into a chunk of meat and into the ballstic gelatin dummy and comparing readings. Of course, even if it does decently simulate the electrical conductivity of tissue, it should probalby go in the footnote about its use on the show, rather than in the main article, since that may well be the only case where anyone cared about its electrical properties. scot 21:05, 17 April 2006 (UTC)

[edit] Properties?

Does anybody know what it's made out of? Gelatin and water obviously isn't the only substance, other wise it wouldn't be able to retain the human-like properites of muscle. mark

It is just gelatin and water--see the link to the FBI's recipe. The imporant feature as far as bullet penetration and expansion are concerned is viscosity. Ballistic gelatin is a good match to muscle tissue, for both humans and game animals. It does not provide any simulation of the skin, fat layers, organs, or any other structures, but then the purpose of ballistic gelatin is not to provide a perfect match, but rather to provide a consistent, repeatable medium for comparative testing. For an example of attempts to provide simulation of structure, take a look at the tests done by John Linebaugh at the Big Bore Sixgun Seminar. They use wet newspaper, which is a tougher medium than gelatin, and they test for DEEP penetration--the Garrett Hammerhead .45-70 load penetrates 55" of wet newspaper[1]. In some tests they also throw in actual bones from recently slaughtered livestock to test the toughness of bullets. Somewhere I have run across an online summary of one of the year's tests, but I can't seem to find it right now; it covers the test conditions as well as the results. Since the focus is large, dangerous game hunting with a handgun, the focus is very much on heavy bullets, large bore diameters, and tough, non-expanding bullets. scot 15:21, 7 December 2006 (UTC)