Test: Double Tap 155 gr Gold Dot vs. Speer 165 gr Gold Dot

[ToddG]

sjc -- Coincidentally, DocGKR and I were discussing this just the other day. There are certainly better approaches, but the one listed above is, as DocGKR pointed out, the standard that's been used for years. Changing it now, if nothing else, would invalidate a ton of historical data.

Measuring only the widest diameter wouldn't make any sense, because if the bullet doesn't expand perfectly evenly then you'd be giving it credit for being, say, 0.6" wide when in many places it's not that wide. One unusual petal sticking out would grossly misrepresent the actual (or average) expansion.

[DocGKR]

sjc3081,

"It seems like the test method is designed to prove and confirm the testers predetermined expectations."

What were those "predetermined expectations"? In the early to mid-1980's, when the RD measurement method was developed, the prevailing theory was that lightweight high velocity projectiles were the best choice for duty use--common LE duty loads included the 9 mm 115gr +P+ and .357 Mag 125 gr JHP.

"I don't understand why the government would invent a way to measure the actual diameter of a recovered round by not actually measuring the diameter of the round."

As noted in the excellent posts above, many recovered projectiles are not of a uniform round shape. The RD methodology attempts to take into consideration the fact that many recovered projectiles are not of a uniform round shape; averaging the largest and smallest dimension is a reasonable attempt to compensate for this factor.

"The more I find out about this jello shooting the more I question the results. "

I am sorry you are so confused. A variety of equally important methodologies are used for terminal performance testing, including actual shooting incident reconstruction, forensic evidence analysis, and post-mortem data and/or surgical findings; properly conducted ethical animal test results; and laboratory testing—this includes the use of tissue simulants proven to have correlation with living tissue. Some individuals seem to be under the mistaken impression that one of these areas is more important than others--this is not the case, as each category provides important information to researchers.

The IWBA published some of Gene Wolberg’s material from his study of San Diego PD officer involved shootings that compared bullet performance in calibrated 10% ordnance gelatin with the autopsy results using the same ammunition. When I last spoke with Mr. Wolberg in May of 2000, he had collected data on nearly 150 OIS incidents which showed the majority of the 9mm 147 gr bullets fired by officers had penetrated 13 to 15 inches and expanded between 0.60 to 0.62 inches in both human tissue and 10% ordnance gelatin. Several other agencies with strong, scientifically based ammunition terminal performance testing programs have conducted similar reviews of their shooting incidents with much the same results--there is an extremely strong correlation between properly conducted and interpreted 10% ordnance gelatin laboratory studies and the physiological effects of projectiles in actual shooting incidents.

The last several years of OCONUS GWOT operations have provided a tremendous amount of combat derived terminal performance information. The U.S. government gathered numerous experts from a variety of disciplines, including military and law enforcement end-users, trauma surgeons, aero ballisticians, weapon and munitions engineers, and other scientific specialists to form the Joint Service Wound Ballistic Integrated Product Team to conduct a 4 year, 6 million dollar study to determine what terminal performance assessment best reflected the actual findings noted in combat the past few years. The test protocol that was found to be correct, valid, and became the agreed upon JSWB-IPT “standard” evolved from the one first developed by Dr. Fackler at LAIR in the 1980’s, promoted by the IWBA in the 1990’s, and used by most reputable wound ballistic researchers.

The JSWB-IPT, FBI BRF, AFTE, and other organizations get to assess an extensive amount of post-shooting forensic data. The whole raison d'être of these independent, non-profit organizations is to interpret and disseminate information that will help LE and military personnel more safely and effectively perform their duties and missions. Physiological damage potential is the only metric that has been shown to have any correlation with field results in actual shooting incidents, based on law enforcement autopsy findings, as well as historical and ongoing combat trauma results. Again, I am sorry if these ongoing efforts in the support of U.S. military and LE personnel are confusing to you, however, they have been proven to work in the real world...

[DrJSW]

Well summarized and succinctly put, DocGKR.

[Jack-O]

It look like about a 10% increase in performance.

The question we have to ask then is, Is it worth the extra flash and recoil to get 10%?

[DocGKR]

While all three loads were acceptable, I'd say the standard Speer loaded 155 gr GD performed the best...

[Marcus L.]

While all three loads were acceptable, I'd say the standard Speer loaded 155 gr GD performed the best...

Yep. It beat out the Double Tap load in the demin test by creating a larger overall wound volume within the first 12".

"Given desirable and reliable penetration, the only way to increase bullet effectiveness is to increase the severity of the wound by increasing the size of hole made by the bullet." -Handgun Wounding Factors and Effectiveness

The FBI protocol tests were designed to maximize ammunition engineering around the human target and when it comes to this model the Double Tap loads offer no measurable advantages. You might say they only offer disadvantages with decreased handling.

[zydeco76]

I want to thank Doc and the devils advocate here. I learned a few things I would not have otherwise. Doc you are an asset to us all.

[DRT]

I've tried to lobby for upgrading our issued duty load to a premium 180gr round like Ranger T-series or HST. Despite supplying all the references and terminal ballistics data that I could find, we're unfortunately still being issued the 165gr Gold Dot. Very disappointing.

[DocGKR]

DRT--FWIW, I personally would not feel bad about carrying the GD 165 gr Gold Dot as a duty load, as it offers acceptable penetration, robust expansion, and reasonable intermediate barrier capability; you could do a lot worse...

[crenca]

On a tangent, my limited testing over a chrony revealed to me Double Tap's 6.8 loads are very consistent, and about 25 fps under SSA's commercial loading. No extra flash or recoil with these loads in my experience.

I have not chronographed their .40 loads but I have noticed more percussion and the brass does travel farther than anything else I have used.

I keep a supply of their 200 grain XTP & FMJ loadings on hand for when I hike in mountain lion country here in NM. Since my G22 is the heaviest pistol I own right now, it will have to do and I like the fact that they load the 200's. Doubt I will ever have to rely on it - at least I hope.

I bet their expansion claims are based on wet phone book testing...