Total wound channel comparisons

[BuckskinJoe]

Permanent cavity appears to be the primary factor in handgun and shotgun projectile effectiveness; so, I did a few calculations on total wound channel for a few of handgun calibers, along with 00 buck and #1 buck.

I believe Dr. Roberts has stated that good 9mm ammunition expands, on average, to about 0.60" while .40 cal. expands to an average of 0.65" and .45 ACP to 0.70". Full expansion occurs in the first one-to-two inches of penetration; so, assuming full expansion for all penetration will not make a material difference.

With 12 inches of penetration in all cases, I get the following results:

17 rounds of 9mm give total wound channel of 57.7 cubic inches.
15 rounds of .40 cal. give total wound channel of 59.7 cubic inches, and
13 rounds of .45 ACP give total wound channel of 60.0 cubic inches.

One round of 3" mag. #1 buck (24 pellets) gives total wound channel of 20.4 cubic inches.
One round of 3" mag. 00 buck (15 pellets) gives total wound channel of 15.4 cubic inches.

Now, with the enormously heroic assumption that in a deadly force encounter a shooter can make all good hits, we get the approximate equalities:

18 rounds of 9mm, 15 rounds of .40 cal., 13 rounds of .45 ACP, 4 rounds of 3" 00 buck, and 3 rounds of 3" #1 buck all yield approximately the same total wound channel.

Another way of looking at it is: 6 solid hits with 9mm, 5 solid hits with .40 cal., 4 solid hits with .45 ACP, and one solid hit with 3" mag. #1 buck all have approximately equivalent total wound channel.

[Zhukov]

Interesting play with the numbers, but the big thing is the statistical probability of getting that subsequent hits goes down exponentially with each shot.

[BuckskinJoe]

Interesting play with the numbers, but the big thing is the statistical probability of getting that subsequent hits goes down exponentially with each shot.

Very intentionally, I did not make or imply any conclusions from the rather simple calculations, but I am inclined to agree that, generally, achieving "good hits" from subsequent shots tends to decrease in probability as shot count increases. However, some might proffer the controllability of a 9mm allows both faster and more accurate follow-up shots.

Personally, I lean toward the side of "bigger holes with fewer shots" mindset, and nothing compares with 12 gauge buckshot in that arena. Consequently, our primary home defense firearms are shotguns--my side of the bed has an 870, and my wife's side has an 11-87, both loaded with 3-inch #1 buck. Shotguns, however, are particularly lousy concealed carry firearms; so, she has a Glock 30 in .45, and I carry a Glock 27 in .40 (a bit easier to conceal.) I do have to put up with her teasing me about my .40 S&W (Short & Wimpy) handgun!

Regardless, the 6-5-4-1 wound-channel equivalency for 9mm, .40, .45, and 3-inch #1 buck seems to me to be a reasonable ballparker.

[DBR]

How did you determine the crush cavity diameter?

It's not as large as the bullet diameter in most cases and there are many variables. I don't think you can assume it is even proportional to the expanded diameter of the bullet and it changes with velocity.

[BuckskinJoe]

How did you determine the crush cavity diameter?

I believe the numbers are in my original post, but, if you missed them: 9mm--0.60" .40 cal.--0.65" .45--0.70"

For buckshot, I used the pellet diameters: 0.30" for #1 buck, and 0.33" for 00 buck.

Cross sectional area is calculated by pi-r-squared, and wound channel volume by multiplying by 12 inches. However, the depth of penetration has no effect on the relationship among the projectiles--it will remain 6-5-4-1 for 9mm. /40 cal./.45 ACP/3" #1 buck (24 pellets) regardless of the depth used.

It's not as large as the bullet diameter in most cases and there are many variables. I don't think you can assume it is even proportional to the expanded diameter of the bullet and it changes with velocity.

If your claim is correct, how much of a projectile's cross section does not produce wounding and does the proportion change for 9mm., .40 cal., .45 ACP and buckshot? What are the many variables that would change the relationships?

Also, your claim that permanent cavity cross section changes with velocity in handgun and shotgun projectiles is an interesting conjecture that I haven't encountered in reputable research I've seen. Furthermore, the velocities of all the projectiles I mentioned are all in the trans-sonic range with little difference among them.

I would be delighted to hear back with reputable data that invalidates the general permanent cavity comparisons I have calculated. It does seem to me that larger diameter projectiles will produce proportionally larger wounds than smaller projectiles and "x" many projectiles will produce "x" times the total wound channel with the same penetration.

[crossgun]

I don’t believe that the human body works in this manner to actually cause a "true" permanent wound cavity or carve out 100% channel. While I am sure the math is correct guess I don’t see the relevance.

It would be great if tissue reacted this way to bullets.

[NinjaMedic]

Could this be better calculated by measuring the volume of water you can pour into the ballistic gelatin after shooting it? With a large enough sampling you could probably get a fairly accurate approximation of the average total wound channel for each round. Has this been done before?

[BuckskinJoe]

Could this be better calculated by measuring the volume of water you can pour into the ballistic gelatin after shooting it? With a large enough sampling you could probably get a fairly accurate approximation of the average total wound channel for each round. Has this been done before?

That is an intriguing idea! My initial question is whether or not ballistic gelatin "retains" temporary cavity, which would skew the results.

Perhaps, Doctor Roberts will weigh in. Again, my whole purpose was to calculate "ballpark" estimates of the relative permanent cavity (crush) wounding capacities of some handgun and shotgun rounds--ceretis paribus. Large sample sizes of controlled experimental results, of course, would give a more accurate picture.

[crenca]

I had always assumed that expanding ammo (even in the case of the latest generation) was not consistent enough for anything but rough/general calculations like this. Still, you are not claiming anything more.

Also, what is the velocity of say #1 buck at 20 yards as opposed to 3? I would think the penetration of buck is very sensitive to distance (more so than pistol ammo).

[BuckskinJoe]

I had always assumed that expanding ammo (even in the case of the latest generation) was not consistent enough for anything but rough/general calculations like this. Still, you are not claiming anything more.

Also, what is the velocity of say #1 buck at 20 yards as opposed to 3? I would think the penetration of buck is very sensitive to distance (more so than pistol ammo).

I used the numbers, I believe, that Dr. Roberts published as average recovered diameters of the best performing current handgun ammunition along with the actual pellet diameters of 00 and #1 buck to get the best central tendency esitmates. #4 buck, because of the greater number of pellets, gives even greater total wound channel, but #4 buck, in gelatin tests, does not exhibit consistent penetration of 12 inches or more; so, I did not include #4 buck.

Agree with your premise that buckshot sheds velocity much faster than handgun bullets, but, for my purposes, in the home, I would never have a shot in excess of 5 yards. Also, I simplified the comparisons by not considering the first portion of handgun bullet penetration before complete expansion, and I did not consider the additional wound channel produced by the wad cup at short ranges in shotgun rounds