Pistol Ammunition Ballistics Part 2

BY Herschel Smith
6 years, 1 month ago

In Oversimplifying Ammunition Ballistics I had an argument with Tam, who is an NRA writer, and she doesn’t like the idea of “flying dimes.”  Ridiculous, said I.  And you can read the rest for yourself.

Today I passed through The Firearm Blog, and normally I like what I see there to some degree, including the comments, but this one just caused me to laugh.

They have a picture of a man (obtained via Facebook) who had a bullet lodged in his head, still visible.  Must have been a squib load, must have been a reload, he must have been wearing a helmet, and on and on the comments go.

Pitiful .45 ACP, said a few.  Shooter should have used something else like the much more effective 9mm.  One commenter said that the .45 ACP penetrates farther than the 9mm, and so there must have been shielding in between the muzzle and his head (like a helmet).  The response to this commenter was that he lost all respect because he said that the .45 ACP penetrates farther than the 9mm.

Good grief.  So much chaos in one place is mind boggling.  I don’t know how many readers actually dropped by the ballistics tests run by Lucky Gunner that I linked in my original post, but probably not many.  I usually have readers for under two minutes, so blogging is something that must be done where readers can digest quickly.

But after I read those comments, I did a little bit of calculating on those test results for 9mm, .40 S&W and .45 ACP.  Here is what I got for their self defense loads.  I discarded the 2 (two) lowest penetration depths for all three rounds, as they appeared to be outlier data points.

9mm: Average penetration depth = 17.762 inches, standard deviation = 2.777, maximum penetration = 26.5 inches.  This gives a fractional standard deviation (FSD) of 0.156 or 15.6%.  Mass of bullet achieving maximum penetration = 124 gr.

.40 S&W: Average penetration depth = 19.034 inches, standard deviation = 5.637, maximum penetration = 32 inches.  This gives a fractional standard deviation of 0.296, or 29.6%.  Mass of bullet achieving maximum penetration = 180 gr.

.45 ACP: Average penetration depth = 18.867 inches, standard deviation = 5.009, maximum penetration = 31.2 inches.  This gives a fractional standard deviation of 0.265, or 26.5%.  Mass of bullet achieving maximum penetration = 200 gr.

Various bullet masses were used for the tests.  This doesn’t give room for either (a) Tam to claim that lighter weight bullets are “flying dimes,” or (b) the commenter at TFB to claim that .45 ACP penetrates farther than 9mm (at least, not much farther).  It also certainly doesn’t give room to tell that commenter that he has lost all respect of the firearms community.  Such exaggeration is juvenile.

Here is the problem.  An astute Monte Carlo analyst would tell you that these problems haven’t converged.  Most analysts like to see on the order of 5% – 10% FSD before developing any confidence in the system.  There may also be some issues with these rounds, in that there was inconsistent or incomplete expansion of every “maximum penetration” round for each of the three calibers.

More data is needed, and I didn’t run a VOV (variance of the variance) on these samples since the sample size is so small.  The problem needs to converge before developing confidence in the system.  The trouble is that this takes ammunition, ballistics gelatin, denim, test apparatus, and human resources.  None of this is cheap.

There is also the issue of differing masses of bullets, but since the sample size is small for caliber, it’s even smaller for bullet mass within a caliber.  But suffice it to say that lighter mass bullets aren’t flying dimes, and you can examine the data for yourself.

It’s also clear that each round performs well and penetrates far enough to do massive damage (except perhaps for the outlier data points).  Ammunition brand is also a consideration.

The point of all of this is that if you want to make hyperbolic and exaggerated statements concerning much of anything, be my guest.  I prefer to be a thinking man.  And if Lucky Gunner wants assistance in analyzing the performance of any other tests, I’m available.  But I do recommend proper convergence of the data sets.  That requires more shooting.

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  1. On January 17, 2018 at 9:23 am, Frank Clarke said:

    All this talk about ‘penetration’ leaves me feeling a little… I don’t know… curious? I don’t load my own — have never reloaded any ammunition, so I’m far from ‘expert’ on the topic, but…

    If a slug penetrates 19″ into a target that is 14″ deep, it seems to me that that slug must exit out the back of the target still carrying a portion of its original energy with it, and that energy is wasted.

    I want a slug that LODGES inside the target having expended every last erg it had when it arrived at the target. There is such a thing as ‘over-penetration’. What am I not seeing?


  2. On January 17, 2018 at 10:01 am, Herschel Smith said:

    Atta boy Frank. I have the best readers on the internet, yes?

    When I posted this, I actually thought about going back and amending or adding a paragraph to the end to explain what my biggest concern would be for these “flying dimes” as Tam calls them.

    Possible over-penetration and failure to deposit the full energy in the target. I also thought about making all of this part 3 of this subject for another post.

    There appear to be no “flying dimes” in modern powders and ballistics, especially for +P loads. Of course, modern ballistics also stretches the specs for SAAMI pressures, forcing manufacturers to think hard about their manufacturing and fabrications and materials.

    What an interesting subject, worthy of much more study and conversation.

  3. On January 17, 2018 at 10:06 am, TFA303 said:

    That’s a common question. The key is that handgun rounds’ damage mechanism is much more dependent on what it penetrates, as opposed to rifle rounds, which do far more damage because they transfer enough energy to destroy tissue surrounding the bullets’ path. Or, as Larry Correia (inter alia) says, “all handgun rounds suck.”

  4. On January 17, 2018 at 1:14 pm, Bill Robbins said:

    The ballistics are interesting, but the more important factor in this particular case is anatomy. A bullet fired at the front of the head is less likely to penetrate the forehead than, say, the bridge of the nose.

  5. On January 17, 2018 at 1:19 pm, oughtsix said:

    As to “over penetration,” any hunter will tell you that there is no such thing… two bleeding holes (and the exit wound usually bleeds much more than the entry) are better. Of course, hunters are concerned with tracking wounded game but, any bullet which “over penetrates” has to have greater energy (bullet construction and expansion being roughly similar) than one which “dumps all its energy within the target.”

    That through and through wound, with adequate expansion, tears up lot more tissue, causes a greater temporary cavity as well and has a better chance of finding something terminal, such as blood loss. Greater impact tends to create greater expansion, although current design parameters and manufacture tailors bullet construction to weight/velocity/diameter.

    The bottom line is still as it always was: Shot. Placement. is the biggest determinate of effectiveness by a big margin.

  6. On January 17, 2018 at 7:11 pm, Quercus said:

    Given that mere mortals are legally responsible for everything that leaves the muzzle, why the fascination with maximum penetration through flesh? Doesn’t it seem foolish to carry 26″ avg penetration rounds in an urban environment?

  7. On January 17, 2018 at 8:57 pm, Herschel Smith said:


    I would agree with that statement if the average was 26″. The averages computed were: 17.762″, 19.034″ and 18.867″ for 9mm, .40 and .45, respectively. They were all about the same.

    Context sir. The original piece was disputing Tam’s rant where she talked about “flying dimes.” There are no “flying dimes” in modern medium to large bore PD rounds. And as for that matter, .38 SPL performs about the same as 9mm, and as expected, .357 magnum much better.

    And then you saw readers bring up the issue of possible over-penetration, with which I concurred. The problems, however, seem to present themselves on failure to expand.

  8. On January 17, 2018 at 9:20 pm, Maximus said:

    Gentlemen, in terms of a bullet leaving the target or “overpenetration” some say they would like the projectile to stop before exiting the back of the target, I disagree.
    The purpose of the projectile is to lessen the blood pressure of the perp to the point where he is combat ineffective. I or those being protected cannot be further physically harmed by the perp. Bleeding from two holes is superior to one hole, over penetration in terms of innocents a concern of course. The best projectile breaks the skin on the exit side and drops to the ground, spent. It’s all a crap shoot but over penetration drops blood pressure faster.
    Oughtsix has it pegged.

  9. On January 18, 2018 at 1:13 am, Gator said:

    If people are really concerned about over penetration, there’s always frangible ammo. International cartridge corporation makes some that are designed for self defense. Probably won’t do as much damage as a high end hollow point, but they definitely won’t over penetrate, and if they hit a wall or something, especially inside the house, that should be the end of that bullet.

    I carry 9mm hydrashoks. Some friends and I fired a bunch of hollowpoints into sand and dug them out. Sand isn’t ballistic gelatin, obviously, but hydrashoks were the only ones that expanded exactly as they should, every time, from all 3 calibers. Since then, thats all I’ve carried, specifically the low recoil rounds made for smaller framed guns.

  10. On January 18, 2018 at 5:56 pm, pdxr13 said:

    You can’t have too much pistol performance. But, there is a level of “performance” that stops being useful. It’s probably a cartridge smaller than 45-70. I don’t enjoy shooting a snub-nose ultralight .357Mag, but the same cartridge in a 6″ barrel steel pistol (Blackhawk?) is fine. There is good middle ground in most things, where “man is the measure”, leading us to lots of “just right” .30 rifles and .30-.40-something pistols with advances in bullet construction making incremental improvements for specialized situations over jacketed lead. As noted in comments, a perfectly-placed round does’t need anything else. I’m still working on this aspect of perfection, with elevated pulse and empty stomach, in the cold.

    Thanks for the blog.

    rufus thirteen in portlandia

  11. On January 22, 2018 at 6:53 pm, Survivormann99 said:

    “A man can never have too much red wine, too many books, or too much ammunition.”
    —-Rudyard Kipling

  12. On January 23, 2018 at 9:35 am, The Gray Man said:

    I’m assuming the original debate on TFB was about the mythical “stopping” power, whatever that is. I’ve always thought that debating stopping power among pistols is like debating who wins a race between a Volkswagen Bug and a Jeep Wrangler. Who cares? If you’re carrying a certain pistol for the stopping power, then you’re probably driving a Yaris for the awesome horsepower, right? A rifle or shotgun is carried for the effect it has on the target. Pistols are carried because they can be conveniently carried anywhere.

  13. On January 23, 2018 at 12:18 pm, survivormann99 said:

    I am no authority here. I have pistols in both .45 ACP and 9 mm. I cannot speak with any authority about which cartridge is superior, but I am inclined to believe those who say that bullet placement trumps any deficiency in either cartridge.

    Like everyone else, I have read ad nauseum about the U.S. Army’s experience in the Philippines during the Insurrection that led to the development of the .45 ACP. What one author who wrote about this history pointed out is that the much told story always stopped with the Army’s adoption of the M1911.

    He said that the ugly truth was that no one ever mentioned was the fact that the 1911 didn’t stop Philippine Insurrectos either. I will leave it to others to research the matter and determine if this is a fair statement.

    The story goes that a Texas Ranger was at a party. The hostess, seeing the pistol that the Ranger was wearing, walked over and asked sweetly, “Why, Ranjah, are you expectin’ trouble?” In reply, the Ranger drawled, “No, ma’am. If I were expectin’ trouble, I’d have brought a rifle.”

    Only a fool would head to a gunfight with only a pistol. If a person knew that he was headed to a gunfight, if he had “a lick of sense,” he would carry a rifle or a shotgun as his main firearm, depending on the conditions he expected to find at the fight, and a pistol as a backup.

    Nevertheless, it’s a good idea to know which pistol will provide the best margin of safety when the unexpected occurs.

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You are currently reading "Pistol Ammunition Ballistics Part 2", entry #18466 on The Captain's Journal.

This article is filed under the category(s) Ammunition,Firearms,Guns and was published January 16th, 2018 by Herschel Smith.

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