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Penetration vs Expansion

9K views 75 replies 18 participants last post by  Fyrtwuck 
#1 ·
In a self defense situation, I think it's safe to say that penetration is desired over expansion. However, I wonder how many of us carry rounds based on expansion over penetration? This issue has probably been litigated to death before, but I couldn't find it in many forums.
 
#2 ·
IIRC the "standard" is 1.5 times the unfired diameter for being satisfactory. Plenty exceed that.
Usually big expansion means less penetration. The degree of that is the devil in the details.
My opinion is I'd rather have an inch over maximum than an inch over minimum. Judging on all the folks I've picked up off the street and other places, that is my preference.
I'd love to have a 9MM or 40 that expanded to an inch and hit 18 inches consistently, but that is not available just yet. The ammo I use in 40 hits the 15-16 in mark and expands well. The 9MM I landed on expands 1.5 times but hits the 19 inch mark consistently. Some believe that is too much, but they can use what they want.
Cheers
 
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#5 ·
I research my carry ammo for the best of both. I stay away for the light grain weight for caliber rounds, because they usually expand to quickly. The caliber I worried about the most was .380 acp. I know a lot of guys who carry fmj’s instead of hollow point ammo, for fear of HP’s under penetrating. So I’m my micro .380’s I carry underwood non plus P Xtreme defenders ( not penetrators).
 
#7 ·
Water is a fun media, and can tell us a lot. A milk jug is 8 inches, so you got 24+ inches of penetration. Not likely in a live target or 10% ordinance gel.
HST wouldn't be the scream it is, if that were the case.
 
#10 ·
Several months ago, while at my LGS they were all hyping the Liberty 50gr at 2000/fps. Obviously, I was impressed at how light the box was. I bought a box and carried it in my G48. I had concerns about a gun cycling this ammo but thought my Glock would be the best gun I own for that. I knew it wouldn't over penetrate, nor would it expand very well. Good carry for crowded venues?? I've since switched to one cartridge for all guns, Gold Dot 124gr +p.
 
#12 ·
... my LGS they were all hyping the Liberty 50gr at 2000/fps.
AMMO REVIEW: 9mm Liberty Ultra Defense 50 gr JHP


For what it's worth... :)

Best regards,

Bob
 
#11 ·
I research my carry ammo for the best of both. I stay away for the light grain weight for caliber rounds, because they usually expand to quickly. The caliber I worried about the most was .380 acp. I know a lot of guys who carry fmj’s instead of hollow point ammo, for fear of HP’s under penetrating. So I’m my micro .380’s I carry underwood non plus P Xtreme defenders ( not penetrators).
Likewise as I do myself.
 
#20 · (Edited)
Aren’t we supposed to follow the FBI standards for a balance between the two?
All major cartridge manufacturers do exactly that. Accordingly, they typically strive for the FBI's penetration mid-point of 15" (in ballistic gelatin with various barriers) and a minimum expansion of 1.5 times the bullet diameter.

Font Material property Screenshot Parallel Document

Excerpted from: HORNADY’S CRITICAL DUTY AMMO
https://public.ntoa.org/AppResources/publications/Articles/2158.pdf

That said, in the real world, penetration without adequate expansion is preferred over expansion without adequate penetration simply because, to 'stop the threat', the bullet must typically disrupt vital functions... and, without adequate penetration (regardless of expansion), the probability of that happening decreases significantly.

However, the goal of every manufacturer is to produce the 'perfect' cartridge as presented in HORNADY’S CRITICAL DUTY AMMO...

"The “perfect round,” whether fired from a pistol or rifle, will always expand equally (as large as possible relative to caliber) every time it is fired into an opponent (bad guy). It will always penetrate to the desired depth of 12 to 18 inches. It will perform consistently shot to shot. This perfect round will bring on quick incapacitation by either disrupting the central nervous system or quickly lowering the blood pressure of the bad guy."
And, to the best of my knowledge, they're all still working on 'perfection'. :rolleyes: :D

Best regards,

Bob
 
#24 ·
I research my carry ammo for the best of both. I stay away for the light grain weight for caliber rounds, because they usually expand to quickly. The caliber I worried about the most was .380 acp. I know a lot of guys who carry fmj’s instead of hollow point ammo, for fear of HP’s under penetrating. So I’m my micro .380’s I carry underwood non plus P Xtreme defenders ( not penetrators).
Mee too..Also G9, same concept.
 
#25 · (Edited)
So I’m my micro .380’s I carry underwood non plus P Xtreme defenders ( not penetrators).
Considering the following...

380 ACP 68 Grain Xtreme Defender
https://www.underwoodammo.com/colle...-grain-xtreme-defender?variant=18785708179513

BRAND:UNDERWOOD AMMO

SKU:638

TECHNICAL INFORMATION
  • Caliber: 380 ACP
  • Bullet Weight: 68 Grains
  • Bullet Style: Lehigh Defense Xtreme Defense
  • Case Type: Ducta-Bright 7a Nickel Brass
BALLISTICS INFORMATION
  • Muzzle Velocity: 1300 fps
  • Muzzle Energy: 255 ft lbs
  • Penetration: 14 inches
... I'm curious as to how the 14" of penetration was established.

If indeed the penetration is in bare ballistic gelatin, given the bullet's relatively low weight and momentum (68 gr @ 1300 fps, 88 PF), I'm curious as to how it would perform when tested with barriers... and if, in reality, the heavier 'Penetrator' (90 gr @ 1100 fps, 99 PF) would actually perform better.

Just a thought... :)

Best regards,

Bob
 
#26 ·
The way they accomplish that is using a FTM (Fluid Transfer Monolithic) bullet that has an optimized flute geometry. Just a fancy way of saying it has a cross hatch on the meplat. The defenders have a bigger cross hatch than that of the penetrators which are smaller. In either case since both are solid copper, the PWC is larger than a hollowpoint and virtually barrier blind.
Note: there's a notation that they can have 18" of penetration per FBI guidelines.
 
#32 ·
I research my carry ammo for the best of both. I stay away for the light grain weight for caliber rounds, because they usually expand to quickly. The caliber I worried about the most was .380 acp. I know a lot of guys who carry fmj’s instead of hollow point ammo, for fear of HP’s under penetrating. So I’m my micro .380’s I carry underwood non plus P Xtreme defenders ( not penetrators).
 
#36 ·
I'm a huge advocate of ARX ammo. It gives the best of both worlds. Adequate penetration and acceptable expansion. Its a lightweight bullet by design. The lighter grain equates into higher velocity. Its higher velocity equates to a substantial wound cavity comparable to expansion from a heavier bullet. It does all this via hydraulic cavitation which is basically the same principle that the hollow point works on. The downside of a hollow point is short barrels equal slow velocity which in turn equate to minimal to zero expansion of hollow point bullets... factor in the clothing factor which clogs the hollow point you may just as well shoot ball ammo. The ARX round is the game changer. By design the non expanding fluted bullet which is approximately 50% lighter than its lead HP counterpart has an increased velocity for penetration. The fluted end of the spinning projectile, which is pretty much barrier blind, creates extreme cavitation when it enters fluidous material such as the body cavity. That cavitation equates to an expansion the same or better than the equivalent HP working at its maximum capacity. The recoil is much less giving you the ability to do follow up shots quickly as you can get back on target faster.

The only problem is finding the ammo in these crazy times.
 
#37 ·
#40 ·


Only video I could find with the 65gr Underwood Xtreme defender .380 I currently have in my mags.
Very interesting videos, Lucian. Thanks! :)

Best regards,

Bob
 
#51 · (Edited)
The 9mm Ammo Quest series of videos (which includes bare gelatin and 'denim' testing) is some of the the best and most comprehensive comparative testing readily available to the general public.

9mm Ammo Quest
https://www.youtube.com/playlist?list=PLgNSGOEQko_M90AMdRCDMgd-w4Yozc27i

Also, note that the FBI Penetration Test criteria (post #20) does not include ballistic gelatin damage caused by 'cavitation'... the criteria includes simply 'penetration depth'.

'Cavitation' and the damage associated therewith has been studied for decades by the military and law enforcement and has been debunked for service/self-defense cartridges.

Contrary to 'Internet wisdom', the 'cavitation' demonstrated by ballistic gelatin is a characteristic of the gelatin and NOT a characteristic of the human body.

The first 'hint' indicating as such is the calibration depth of the BB... which is 2.95" to 3.74" (with a 0.177” steel BB @ 590 +/- 15 fps).

A 0.177" steel BB @ 600 fps simply doesn't penetrate the human body (or a pork loin :rolleyes:) to near that depth.

The FBI considers the 'dependable' damage caused by the bullet to be the 'crush' cavity produced by the bullet's diameter... no more... no less.

Hence...

"We’re looking for 12-18" penetration, uniform penetration, high bullet weight retention and 1.5 times caliber expansion."

HORNADY’S CRITICAL DUTY AMMO

https://public.ntoa.org/AppResources/publications/Articles/2158.pdf
For those interested in further study, peruse the works of...

Martin Fackler
https://en.wikipedia.org/wiki/Martin_Fackler

Duncan MacPherson, including...

Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma
https://www.amazon.com/Bullet-Penetration-Modeling-Incapacitation-Resulting-ebook/dp/B00L7CSV7E

and the...

International Wound Ballistics Association
https://drive.google.com/drive/folders/0B_PmkwLd1hmbd3pWYVVJeGlGaFE

Enjoy the videos. :)

Best regards,

Bob
 
#52 ·
The 9mm Ammo Quest series of videos (which includes bare gelatin and 'denim' testing) is some of the the best and most comprehensive comparative testing readily available to the general public.

9mm Ammo Quest
https://www.youtube.com/playlist?list=PLgNSGOEQko_M90AMdRCDMgd-w4Yozc27i

Also, note that the FBI Penetration Test criteria (post #20) does not include ballistic gelatin damage caused by 'cavitation'... the criteria includes simply 'penetration depth'.

'Cavitation' and the damage associated therewith has been studied for decades by the military and law enforcement and has been debunked for service/self-defense cartridges.

Contrary to 'Internet wisdom', the 'cavitation' demonstrated by ballistic gelatin is a characteristic of the gelatin and NOT a characteristic of the human body.

The first 'hint' indicating as such is the calibration depth of the BB... which is 2.95" to 3.74" (with a 0.177” steel BB @ 590 +/- 15 fps).

A 0.177" steel BB @ 600 fps simply doesn't penetrate the human body (or a pork loin :rolleyes:) to near that depth.

The FBI considers the 'dependable' damage caused by the bullet to be the 'crush' cavity produced by the bullet's diameter... no more... no less.

Hence...

"We’re looking for 12-18" penetration, uniform penetration, high bullet weight retention and 1.5 times caliber expansion."

HORNADY’S CRITICAL DUTY AMMO

https://public.ntoa.org/AppResources/publications/Articles/2158.pdf
Enjoy the videos. :)

Best regards,

Bob
You aren't going to get very far here, or many other places trying to inject logic into an ammo discussion.
Gel is a great medium, the people who do testing for a living know what the data means. It isn't a 1:1 comparison, it doesn't show tissue damage, other than the permanent cavity (that is even subjective) , and a pistol round just won't do what a rifle round will. The magic number seems to be about the 2200 FPS mark for temporary cavitation to start making it's presence known. So, anything under 2200 fps has to be touched by the projectile for damage to occur, and the better at slicing, cutting and tearing, the better.
You want to see what they do? Cadaver studies. They happen and you will never see it on the interwebs, or even talked about often, for a number of reasons, but don't think they haven't been done to nauseum and the comparisons aren't over documented, measured and compared.
That is how they know that XXX in gel = YYY in a live target.
 
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#58 ·
That one can result in bans. :confused:
 
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#76 ·
I know the discussion is about round performance, but part my career job experience was plugging bullet holes. I’ve seen on scene results from nail guns to shotguns and while performance is important, where the projectile hits is important too.

The worst non fatal single round injury I’ve ever treated was caused by a 45 ACP. I have no idea of what type of bullet it was, but I remember seeing ACP brass on the ground. It was a drug deal gone bad and a woman had been shot in the upper thigh.

When we got to her she was sitting in a recliner with a towel wrapped around her leg like a tourniquet. She was holding it in one hand while calmly holding a glass of scotch in the other.

She was wearing dark pants and when we touched her leg for the assessment our hands were soaked in blood. We cut her pants leg off and there was a huge cavity in her thigh about the size of my fist with the femur and tendons exposed. If the round had been closer to the inside of her leg, it would have easily severed the femoral artery.
 
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