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CougarRed
06-14-2013, 08:59 AM
Hi Doc

I've followed you from the Tactical Forum days 10+ years ago. Thanks for all your hard work in the ballistics arena!

Preamble: I know penetration (and placement) is paramount. Here's my question: When you are testing ammo, what are your expansion minimum guidelines?

The reason I ask is I saw an old post of yours (Sept. 2000) concerning some testing you did on lighter weight 40S&W rounds:

All of the 135 gr to 165 gr .40 S&W bullets either failed to meet minimum penetration (12") or expansion (0.65") guidelines.

That led me to dig a little further, and I found another old post (Jan. 2001) that referenced your 1994 article Comparison of the Terminal Performance of 9, 40 & 45 JHP, and went on to explain:

The ideal handgun bullets for law enforcement and military special operations . . . have consistent expansion (approximately 0.60 inches for 9 mm, 0.65 inches for .40 S&W, and 0.70 inches for .45 ACP) without fragmentation, core-jacket separation, or significant weight loss.

I can't find a copy of your 1994 article, so my question is: when ammo testing, are your expansion minimum guidelines 0.60" for 9mm, 0.65" for 40S&W and 0.70" for 45ACP?

****************

Likewise, I can't seem to locate a copy of your 2000 article Terminal Performance of .38 Special and .380 Hollowpoint Bullets Intended for Law Enforcement Back-Up and Off-Duty Self-Defense Using 10% Gel as a Tissue Simulant.

Do you have a minimum expansion guideline for .380 and 38 special? Is it 0.50"?

The reason I ask is that I saw you once commented favorably about the 110 Corbon DPX standard pressure 38 special load which tested at:

.38 Sp Corbon 110 gr JHP DPX (using Barnes XPB all copper bullets), ave vel=1021fps
BG: pen=13.0"; RD=0.52", RL=0.52", RW=109.5gr
4LD pen=12.4"; RD=0.52", RL=0.51", RW=109.7gr

Many thanks!

CougarRed
06-16-2013, 02:47 AM
Doc,

I'm just trying to understand your criteria behind statements such as:

Round A exhibits adequate penetration and expansion for law enforcement use;

or

Round B exhbits unacceptable terminal performance for law enforcement use due to inadequate penetration or inadequate expansion.

I know such statements are based on multi-shot averages (at least 5, preferably 10) through standardized barriers (such as 4-layers of denim) and into approved test media (e.g. not SIM-TEST).

And obviously, you've been consistent in adhering to the FBI 12 inch minimum penetration standard for all rounds. But the expansion standard has to vary by the starting size of the caliber. So when you say Round B has inadequate expansion, what are the minimums you use by caliber?

Is it:

0.70" for 45
0.65" for 40
0.60" for 9mm
0.50" for .38 special
0.50" for .380

Clarifying this issue will help all of us understand exactly what you mean when you say Round A has adequate expansion or Round B has inadequate expansion.

Many thanks.

DocGKR
06-16-2013, 12:45 PM
Unlike the 12-18" penetration guidelines, there are no hard and fast recommendations for expansion. Some LE agencies want at least 1.5 times the original diameter (ie. .38/9mm = 0.53", .40 = 0.60", .45 = 0.68"), others set agency specific minimum average expansion requirements in their ammo contracts (ex. 9 mm = 0.60", .40 = 0.65", .45 = 0.70"), still others don't set any limits. We use whatever standards an agency sets for a specific test. Consistent performance across multiple shots with various intermediate barriers is far more important than any absolute expansion threshold, assuming adequate penetration is maintained.

CougarRed
06-16-2013, 11:02 PM
Unlike the 12-18" penetration guidelines, there are no hard and fast recommendations for expansion. We use whatever standards an agency sets for a specific test. Consistent performance across multiple shots with various intermediate barriers is far more important than any absolute expansion threshold, assuming adequate penetration is maintained.

Thank you very much Doc! Makes sense.

BTW I stumbled across something else interesting recently: the 1987 FBI Wound Ballistics Workshop (https://www.ncjrs.gov/pdffiles1/Digitization/113821NCJRS.pdf)!

Do you or any forum members have any insight on how or why the penetration minimum changed from the 1987 FBI Wound Ballistic Workshop (10-12" minimum) to the 1989 FBI paper by Urey Patrick (12" minimum)?

The 1989 paper cites the 1987 workshop for support on the 12" minimum (see FN36 of the 1989 paper), so I was surprised to read that the 1987 paper actually said (near the end):

"The single most critical factor remains penetration. A handgun bullet MUST reliably penetrate 10-12 inches of soft body tissue at a minimum, regardless of whether it expands or not. Penetration up to 18 inches would be even better. If the bullet does not reliably penetrate to these depths, it is not an effective bullet for law enforcement use."

Perhaps by 1989 the FBI decided to hold the ammo manufacturers to a higher standard? Perhaps the FBI worried if they said 10-12 inches, they knew it would be interpreted as 10 inches and they wanted to err on the conservative side? Hell, maybe they figured the trend was for people to get fatter, and they wanted to set a minimum that would not become obsolete from obesity? LOL

DocGKR
06-16-2013, 11:28 PM
Your last paragraph is correct; the FBI supervisor wanted a single hard and fast number as a bottom line minimum, so the more conservative 12" was adopted--a good thing given the increasing BMI of the American population.

buckskinjoe
10-06-2013, 08:23 AM
Your last paragraph is correct; the FBI supervisor wanted a single hard and fast number as a bottom line minimum, so the more conservative 12" was adopted--a good thing given the increasing BMI of the American population.

Hey, now...I resemble that remark! :D