@nate45
According to Rob, 9mm is the way to go. Its hard to fault the logic behind his reasoning
Actually, it's easy to fault the logic behind his reasoning, since he doesn't really use logic. He presents facts in such a way that they support his preconceived conclusion.
He appeals to science in his first point, about recoil, and proposes that the difference in felt recoil is significant.
He then states that 9mm guns have higher capacity. They do, and on the face of it this might sound significant.
He then resorts to hearsay anecdotal evidence to dismiss any difference in stopping power/wounding potential as "negligible", rather than using science (as he did in the first point) to compare.
One could just as easily say that the negligible difference in felt recoil and capacity do not justify the sacrifice in stopping power that you get with 9mm.
Examining the points:
9mm has less recoil than .40 S&W? Yes, it does -- but is it significant? Having fired a lot of different caliber weapons, I can say that I didn't find much difference between 9, 40, .45 ACP, or .41 AE. Certainly not compared to .357 magnum in a revolver, which was a significant increase in recoil. And keep in mind that if you are a good shooter, and have gotten over basic recoil flinch, recoil won't affect the speed or accuracy of your first shot, only successive shots. And the first shot should be the most important, the one where you seek to hit the bad got, stop the bad guy, and end the encounter.
9mm has more capacity than .40? Yes, it does -- but again, is it significant?
Typical capacities are 17 for 9mm/15 for .40, or 15 9mm/13 .40. That means a 9mm holds 13-15% more ammunition than a .40 cal. That sounds significant on the face of it -- but is it really? How often in a gunfight are rounds 16 and 17 really needed? If you were to analyze that statistically with the data from all defensive shootings (not military combat, where volume of fire dictates that far more shots will be used), you'd probably find that the last two rounds in a high-capacity magazine are rarely ever fired. That would lead me to believe that the capacity difference between 9mm and .40 is "negligible", to use Rob's terms.
The difference in wounding potential is "negligible"? Had Rob used physics, which he appealed to in his first point, rather than arbitrarily dismissing .40 S&W's advantage here, his argument would have been greatly weakened. While obviously there is a great deal of variation in the specific loads used, one thing that is constant is bullet diameter, which determines both cross-sectional area (ie, size of the hole it makes) and bullet volume and mass.
Using the formula for area of a circle (math and science, something Rob conveniently skipped!), you find that .40 has 23.4% more cross-sectional area than 9mm. That doesn’t sound “negligible” to me, but more like “significant”. This means that the cylindrical part of the bullet will have 23.4% more volume. The tip is harder to calculate, but let’s assume the difference in volume will be the same (it will actually be greater). So, in absolute terms, .40 will always make a larger hole in it’s target.
With more volume to work with, and therefore more mass, .40 will also probably hit harder and penetrate further. It also has more kinetic energy. Let’s look at some typical figures for the two rounds:
124 grain 9mm @ 1200 ft/second = 382 foot-pounds of energy
155 grain .40 @1205 ft/second = 500 foot-pounds of energy
I picked these because they seemed middle of the road in terms of bullet weight and possible velocities. Note first that the .40 caliber bullet is 25% heavier than the 9mm – which corresponds closely with the figure of 23.4% more volume. Second, note that the velocities are essentially the same. Third, note that the kinetic energy, the “end result”, is 30% greater in the .40. I would call this a significant difference, not a negligible one.
If you were to use +P or +P+ loadings for the 9mm, you would increase your kinetic energy, but at a cost of increasing your felt recoil (you can’t get away from physics), which reduces the supposed advantage of the 9mm, and also a cost of lowered bullet mass (which may decrease penetration, or at least render it equal to the normal 9mm loadings). And what’s to stop someone from coming up with a “+P” loading for the .40 S&W? With the increased diameter and volume of the cartridge, the larger is always going to have more potential. No one ever argues that .38 Special is “just as good” as .357 magnum, so why do they argue that the smaller 9mm is the equal of the larger .40 S&W and .45 ACP?
Bottom line: there’s no clear proof either way of which is superior in a gunfight. The 9mm may recoil a little less, the .40 will hit a little harder. There are advantages and disadvantages to both. Use whichever one you like best.
