Crime Lab Innovates Gelatin Tests

Going Ballistic!

GUNS: Testing handgun ammunition for the Dallas Police Department back in the early 1970s required some good old ingenuity. Any new ammo the crime lab recommended would have to work well in both service sidearms and snubnose revolvers.

My first column and the next one will relate the little-known contributions of the Dallas County Crime Lab to scientific testing of police handgun ammunition. I was the firearms forensics examiner in the crime lab in the 1970s and '80s. At the beginning of my tenure, the standard test of power was how many 7/8-inch pine boards a bullet could penetrate. This was a terrific test if your self-defense concerns involved marauding lumber.

Then there was Maj. Gen. Julian S. Hatcher's Theory of Relative Stopping Power, a strict calculation based on general conditions. Like the pine-board test, it did nothing to address expanding bullets. These older methods of estimating bullet success have been beaten in print more than any dead horse, so I'm not going to review them here.

Setting A New Standard
The Dallas County Crime Lab's involvement started innocently enough, and we had many of the resources to accomplish it. We only needed a "trigger event," and it all started with a phone call.

Although an agency of Dallas County, the lab did most of the crime-lab work for the City of Dallas Police Department, and it had a lot of friends there. One was a gruff veteran captain who was responsible for buying arms and ammunition for the department. At the time, Dallas issued its officers a .38 Special Smith & Wesson Model 10 and whatever lead roundnose (LRN) ammo came in with the best price; this was a situation the captain inherited from his predecessors. He wanted a smarter way to make ammo purchases.

My phone rang one morning in 1972, and I heard the captain's distinctive drawl. "Hey, Allan! I've got this S.O.B. salesman from Winchester sitting across from me trying to sell me a new .38 Special load. He claims New York City is using it." The words "New York City" struggled off his tongue with the same tone used in a famous picante sauce commercial. "You got any way to tell me if this idiot is lying?" The good captain always put direct communication above the social niceties.

I said I'd see what we could do. The Medical Examiners' Office, with whom we shared facilities, had just hired Dr. Vincent J. M. DiMaio from the Armed Forces Institute of Pathology (AFIP). He told us how AFIP tested military ammo using ordnance gelatin.

AFIP made long blocks of gelatin using the then-standard 20 percent concentration. A high-speed motion-picture camera captured a side view of the bullet's dynamic effect at hundreds of frames per second. Then AFIP reviewed the resulting 16mm film on a frame-by-frame basis with image analysis equipment. This determined the volume of the temporary wound cavity produced in the first 15 centimeters (just under 6 inches) as the bullet traversed the block. The theory was that any penetration past 15cm was no longer in a human's internal organs. They worked out that the volume of the cavity was directly proportional to the amount of kinetic energy (in foot-pounds) transferred from the bullet to the block. Incidentally, AFIP never referred to stopping power; it called the results "wounding ability."

We wanted to perform similar tests, but we faced a big hurdle: The expensive equipment that AFIP used was grossly outside our budget. Anyone who worked for county government back then knew it was easier to get a new bulldozer for the road district office than crime-fighting hardware for the lab. It fell to me to see if there was a low-tech way to determine energy transfer--and therefore the relative volume of the temporary wound cavity--with hardware at hand. With the exception of test handguns and a decent ammo budget, the best tool we had was an ancient Oehler Model 10 chronograph with a pair of wood-framed photoelectric screens with 12-inch sensing areas.

After months of crime-lab testing, the Dallas Police Department adopted a hollowpoint service load. The box lacks the +P designator because that standard did not exist in 1973.

Without imaging gear, we could not do a direct measurement of the first 15cm of a long gelatin block. Our solution was to cast blocks to size, making one dimension exactly 15cm. We managed to acquire a professional kitchen mixer for the gelatin, and we were on our way.

Direct determination of energy transfer meant measuring the bullet velocity as it entered the block and as it exited. We had but one chronograph then; thus, simultaneous entrance and exit velocities were not possible. So the first series of tests involved shooting 10 rounds for velocity at 15 feet and calculating the average kinetic energy. We then placed a gelatin block at 15 feet with the chronograph screens behind to read exit velocity, and we fired again. Averaging 10 exit shots, figuring the retained energy, and simple subtraction should provide an energy transfer number.

To see if this cobbled-up rig would work, we had to test AFIP's only two handgun data points: the 9mm Luger and the .45 ACP. Based on AFIP's photo-interpretation system, the transfer numbers were around 110 ft-lbs for the 9mm Luger FMJ and 120 ft-lbs for the .45 ACP FMJ. Our first firing tests showed that our low-tech rig gave energy transfer numbers within 2 to 3 percent of the very pricey AFIP setup. We had the test system we needed.

The Tests
The Winchester salesman left the captain some samples of the then-new .38 Special ammo, a 158-grain lead semiwadcutter (SWC) at standard velocity. The most basic need of the test was to compare the wound cavity volume of the proposed SWC round to that of LRN ammo. We had plenty of gelatin, time set aside for testing, and a keen desire to see what this new test could reveal. After all, the ammo industry was just beginning to react to the Super Vel hollowpoints by Lee Juuras. We bought-- and scrounged--enough to have 15 ammo types representing various bullets and velocity levels. It's a good thing we did; the final recommendation was not the load the salesman proposed to the captain. A selection of the tested .38 Special loads is listed in the accompanying chart ranked by relative wound cavity volume.

We selected an S&W Model 15 revolver with a 4-inch barrel as the test platform and started with several brands of standard-velocity 158-grain LRN ammo. All produced similar wounding abilities of roughly 75 ft-lbs transferred to the blocks. The testing was entirely comparative, so the consistent performance l

evel of LRN ammo became the baseline to which other ammo types would be judged. According to the AFIP criteria, ammo transferring 150 ft-lbs produced a temporary cavity twice that of the .38 LRN producing 75 ft-lbs.

Next we tested the Winchester load the salesman had left plus other SWC loads at both standard and high velocities. At standard velocity, the SWC posted a small but statistically insignificant advantage over the LRN loads. At what today would be .38 Special +P velocities--the +P indicator was not standardized until 1974--the SWC showed a modest advantage, posting transfers of around 95 to 135 ft-lbs depending on make and velocity. For giggles, we shot some 148-grain hollow-base wadcutter ammo; it consistently hovered at 145 ft-lbs transfer.

We couldn't resist shooting one of the old police favorites, the 200-grain lead RN. One brand transferred less than 60 ft-lbs. Another managed to transfer 85 ft-lbs because its odd nose profile caused it to tumble violently almost as soon as it entered the gelatin.

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.38 Special Gelatin Test Results

Ammo Type:Entrance Velocity (fps)Entrance Energy (ft-lbs)Exit Velocity (fps)Exit Energy (ft-lbs)Exit Transfer (ft-lbs)Relative Temporary Cavity Volume
158-gr. LRN776211629139731.0
200-gr. LRN664196559139570.8
158-gr. LSWC Std. Vel.804227623136911.2
158-gr. LSWC High Vel.9303046911681361.9
Super Vel 110-gr. JHP1089290348302593.5
Winchester 158-gr. LSWCHP951317399562613.6
Norma 110-gr. JHP1134435413433925.4

Commercial jacket hollowpoint and softpoint bullets had been around only a few years when we agreed to do the tests, and we made sure they were well represented. From prior water expansion tests, we knew that some early hollowpoints were better dubbed "selling points," defying expansion in any medium less dense than brick. Others were pretty impressive; the original Super Vel 110-grain JHP trotted through the screens at 1,090 fps, expanded nicely, and transferred 260 ft-lbs. That's about 3.5 times the wounding ability of the baseline LRN load.

There were a few surprises. A Norma 110-grain JHP left the revolver barrel at over 1,330 fps and transferred 390 ft-lbs. We later discovered this was decent performance for .357 Magnum HP bullets! The tests also showed that jacketed softpoints--popular back then as being "noncontroversial"--did not expand. Unless driven at velocities no factory would dare to sell in a .38 Special cartridge today, softpoints were mostly middle-of-the-pack performers.

The top performers tended to cluster in the 200 to 275 ft-lb transfer range. We were expected to make a single product recommendation and knew we had to look at more than a single parameter to reach a viable answer.

Second-Order Effects
We crime-lab guys were shooters, and two of us were certified firearms instructors. We felt qualified to explore other factors that affected how the average cop used and reacted to his sidearm. I won't go into the details here, but be assured that many of these, such as recoil, were subjective factors and thus received subjective review. However, we had enough shooting experience to believe that we nailed these pretty close to what the average officer would need.

We considered recoil, muzzle flash as photographed in darkness, expansion in snubnose revolvers, point-of-impact shift in revolvers with fixed sights, exit velocity, effects on automobiles--we found you can't kill a car with a .38 Special--and ricochet potential. All these were added to the hard data from gelatin testing as we moved toward a recommendation.

The Lab's Recommendation
Being the chief "wordsmith" among us lab rats, I got the job of writing it up. The Properties Department captain called and said he wanted

one of us there when he presented the report to the Chief of Police and his senior staff. Someone tossed me the car keys.

I walked into the conference room, and the captain said, "You're doing the presentation."

I hadn't seen so much brass since my last visit to an ammo plant. I presented our recommendation: the Winchester 158-grain lead hollowpoint semiwadcutter (code W38SPD), which would today be a +P load. It stood out from the pack with a 260 ft-lb energy transfer, low exit energy, a point of impact very close to the old duty ammo, relatively decent performance on car windshields, and the ability to expand its diameter when fired from a snubnose revolver. It alone had all the right attributes.

Chief Don Byrd asked his staff if there were any questions or objections. There weren't any, and Byrd turned to the captain and said, "Buy it. Now."

The ammo was quickly bought and issued. We nervously kept our ears to the ground for reports of its use. As they came in, we found that the new cartridge not only was doing a superb job when it was used in earnest, but it also gave many officers a new confidence in their issued sidearms.

The success of the initial test program was sufficient for us to obtain grant money for better equipment, including a ceiling-to-floor steel bullet trap and a matched pair of lab-quality Oehler ChronoTachs with large photoelectric screens. With this new gear, we could take simultaneous entrance and exit velocities, allowing much more diligent analysis of data sets. We started testing every kind of handgun ammunition a peace officer might conceivably carry from .22 Long Rifle to .45 Colt.

As we advanced with the new gear and reviewed more and more police shootings, we realized that we had recommended the right cartridge to the Dallas Police for the wrong reason. I'll explain why next month.

Editor's Note: Allan Jones is the newest addition to the Shooting Times stable of writers. Former Dallas County Crime Lab forensic firearms examiner and editor of Speer Reloading Manuals 12 through 14, he joins the staff as ballistics editor.

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