Guns & Outdoors Forum

With relatively modern advances in 9mm ammo and Glock's pre-eminence as a sidearm, what would Col. Jeff Cooper recommend as a firearm and cartridge combo? Yes he recommended a 1911 in .45 ACP, but I remember him speaking highly of 230 gr. FMJ ball as a fight stopper 9 out of 10 times, improving to 95% when you used a nonexpanding truncated cone profile.

And the Mozambique drill came about because the shooter was using 9mm ball.

Without data, “facts” spoken by vaunted gun writers are speculative BS. What data supports the 90 and 95 percent claim? What’s the sample size? What are the details of the gunshots?


Yes. Yes I am questioning the teachings of famous writers.

I question it, too. But, considering actual modern data about 9mm, the comparison with his selected. 45 ammo becomes relevant.

“As we used to teach in the spook business, carry a 25 if it makes you feel good, but do not ever load it. If you load it you may shoot it. If you shoot it you may hit somebody, and if you hit somebody – and he finds out about it – he may be very angry with you.” -Jeff Cooper

breamfisher wrote: ↑Thu Jul 02, 2026 4:52 pm I question it, too. But, considering actual modern data about 9mm, the comparison with his selected. 45 ammo becomes relevant.

But the comparison isn’t relevant if we don’t have his 45 data.

CPJ 2.0 wrote: ↑Thu Jul 02, 2026 5:46 pm

breamfisher wrote: ↑Thu Jul 02, 2026 4:52 pm I question it, too. But, considering actual modern data about 9mm, the comparison with his selected. 45 ammo becomes relevant.

But the comparison isn’t relevant if we don’t have his 45 data.

If you're trying to disprove his data or an advocate of the .45 is discounting the 9mm data, sure.

But, if both sides accept the effectiveness data of the other? Now both are saying modern 9mm is as good as or better than .45 ball, and can discuss the merits of each cartridge and platform.

I know. This is the modern day. Even if both sides have good data, it doesn't matter.

.45 in theory makes a bigger hole. 9mm has higher capacity and makes more holes. Bigger overall hole area, or more chances to miss?

I say, carry what you are comfortable and proficient with. If you cant shoot a .45 well, what good does it do to carry it? With modern ammunition and component options I dont really feel there is a whole lot of effective difference in use between 9mm, .40, and .45.

I'll stick with the caliber that John Wayne used to capture the Falklands!

I’ll buck the system. Having shot various things with all three………I still prefer the .40 S&W over the other two.

Pretty heavily in my nerdy wheelhouse. . .

As for the gun, Cooper was a big fan of the CZ-75, which, in original, non-clone format was pretty much made of unobtainium in America until near the end of Cooper's life. The market failure Bren 10 10mm that he was an early proponent of was essentially a CZ on steroids. Then again, once they started making good 9mm 1911 platforms, Cooper probably would have stuck with what he championed.

Dunno. Cooper probably would have really come to appreciate Glocks had he spent more time with them or got into the internals. I pretty much divide semi autos into three categories: (1.) 1911's, (2.) Glocks, and (3.) probably not worth my time. This is because 1911's and Glocks are very much about simplicity and not requiring much if anything in the way of special tools to work on and keep working, and if you build them to mil spec and don't eff with them, they pretty much keep working. It took 70 years for Gaston Glock to show up with something simpler and more bomb-proof than the 1911, and the current industry has been pretty much just struggling to not infringe on Glock's patents while wrapping their less-capable, over-complex machines in bells and whistles to make them appeal to the vast class of shooters who think buying a pair of Nike Air Jordans will make them a great basketball player.

As to ammo:

The 9mm was the round that got the bulk of the modern (post-1986) wound ballistic science thrown at it, and was therefore the greatest beneficiary. If you agree with the FBI's protocol which states that "ideal" is that which penetrates 12"-18" in gelatin after defeating any real-world intermediate barriers (clothing, interior building materials, auto glass and sheet metal) and expands to about 1.5x original diameter during the trip, the 147 grain JHP's do that probably better and more consistently than anything else. That the guns don't kick much, don't wear out prematurely, hold a lot of bullets, and you can get some really good small ones chambered for it is just icing on the cupcake. Cooper was a practical fellow and would have eventually seen this, but you can't blame a guy for being raised in the era of manly men and "STOPPING POWAH", nor can you blame him for dying in 2006 as the major shift from .40 back to 9mm was only starting to gather momentum.

The .40 doesn't do QUITE as well on penetration numbers, but it has proven it's ability to work. It had the sales advantage of being "NEW!!" (ooooooh! ahhhhhhh!), and the practical advantage of being introduced WITH the new hollowpoint technology, so there never really was a "bad" bullet for it, at least as far as top-shelf, major-brand duty ammo went. The irony is that by the time it hit the market, the 9mm was fixed - it just took 20 years for the data to sort itself out in the market "hive mind". The .40 worked well - for a time - but the reality was it beats up guns and beats up shooters, and all the big manufacturers went through their own pains of massive design revision to deal with this. I changed A LOT of tired parts and burned A LOT of extra ammo remediating recoil-shy operators. I learned to hate the round with a pretty fiery passion for that reason. Again, Cooper was pretty close to dying as all of this was coming to light, but the guy was a military officer who would have understood those crappy logistics once presented with them.

If we want to discuss the 10mm which Cooper had a hand in creating, it was grown out of widely held "STOPPING POWAH" theories we now hold to be flawed; the handgun technology of the mid-to-late 1980's wasn't really up for the pounding it dished out; and as a round that was designed "by Operators, for Operators", it was never going to do well with the rank and file who train only when mandated to.
The .45 tends to lag a little behind in penetration numbers when you turn it into a hollowpoint. This would be easily solved by hitting it with a little bit more of the "SCIENCE!" that improved the 9mm, but this doesn't seem to have happened. As such it tends to open up a real big parachute and stop within the bottom half of the "acceptable" 12"-18" depth. Now, flat point, non-expanding cast or FMJ's are another story - - they'll penetrate a solid YARD of gelatin and leave a wound track similar to a 9mm HP (albeit longer), but if you're one of the folks who lives in constant fear of "over" penetration, it's probably not the way to roll. It would benefit from a better HP, but the market demand probably isn't there for it to be worth engineering one. Cooper wasn't daunted by the lack of magazine capacity for two reasons (1.) it was what he grew up on, and (2.) he was very much of the mind that if you can't get it done in the time it takes to go through 8 rounds, you probably aren't going to get it done with 16.

Generally, if you start with the same brand of heavy-for-caliber modern HP in each of those three cartridges and shoot three equally built crack-heads in the same spot with one of them, you'll be equally satisfied with the result, and the coroner won't be able to tell any difference in what it was until he actually recovers the bullet and starts weighing and measuring.

Now, if you'll bear with a little more of my nerdiness. . .

I believe it was Marshall and Sanow who were compiling stats that gave us the "One Shot Stop" figures. With basically the same modern HP's we're discussing, they were coming up with (roughly, and from memory), about 89% for 9mm, 92% for .40, and 94% for .45. Easy enough to interpret on the surface, but I think it's a little flawed for this reason:

The modern rounds are leaving basically equal wound tracks and are probably taking the fight out of the target with equal ability, HOWEVER, the .40 and .45 take longer to come out of recoil and you are more likely to perceive that your threat is down once you finally do. With about 40% less recoil, the 9mm is back on target faster and you can deliver a second, third, or fourth shot before you perceive that the first one did the job. This does NOT mean that the 9mm is less effective; it just means that it statistically won't compile as many "one shot" stops.

The current argument that's driving 9mm sales is that you can get two equally effective holes for the price of one.

But nerdier still - and why I've gotten pretty cynical on the whole caliber debate:

I'm part of a group of folks over on Castboolits who geeked out on British military revolver theory between about 1890 to 1940. Specifically, I really wrung out the capabilities of the various 220 to 265 grain options for the .455 Webley and the 200 grain option used in its later .38 S&W little brother. These are all slowpokes in the 600-700 fps ballpark. Granted, I wouldn't choose them for the modern problem of defeating automobile windshields, but for the standard human wrapped in standard clothing, I came away pretty confident they'd perform about as well as what we have now. For that matter, so would a .44 round ball out of a cap and ball 1860 Colt.

So, while it's hard to give a firm answer to the question of WWJCC? (What Would Jeff Cooper Carry?), I can certainly see him in a Glock shooting 9mm for the simple reason that both work, but a 9mm Combat Commander would be completely in character and mindset.

With the advances in ammo technology, maybe we need another round of the "Strasbourg Tests".

They took the "speculation" out of the equation.

Gel is gel. Pigs are pigs. Deer are deer.

If we want good results, we need crackheads. Real life human crackheads. Both medicated and non medicated. There’s a surplus in California. Reduces crackhead population, and gives real data not subject to boomerfudd lore and “my brother law one shot….” Seems like a win win to me.

Crackheads are a bit smaller than the average human, therefore your results may be skewed.

You wouldn't use a varmint bullet on an elk, would you?

CPJ 2.0 wrote: ↑Fri Jul 03, 2026 6:07 pm Gel is gel. Pigs are pigs. Deer are deer.

If we want good results, we need crackheads. Real life human crackheads. Both medicated and non medicated. There’s a surplus in California. Reduces crackhead population, and gives real data not subject to boomerfudd lore and “my brother law one shot….” Seems like a win win to me.

Nonmedicated crackheads are generally horizontal on a hard surface. That would skew test results!

Just shoot skinny pigs.

Or Missouri deer!

CPJ 2.0 wrote: ↑Fri Jul 03, 2026 6:07 pm Gel is gel. Pigs are pigs. Deer are deer.

If we want good results, we need crackheads. Real life human crackheads. Both medicated and non medicated. There’s a surplus in California. Reduces crackhead population, and gives real data not subject to boomerfudd lore and “my brother law one shot….” Seems like a win win to me.

What would I pay to be in a chase car carrying the autopsy kit, wearing a Tyvek suit to prevent crack exposure, just for the ability to say that I'm "following the science"?

Next question. . .if you mixed meth into your ballistic gel ("get me out a block of the Breaking Bad blue") to the standard concentration in an addict's bloodstream, would that gel then be "calibrated"?

The argument is always, ''Advancements in bullet technology makes the 9mm equal to the .45 now.'' Those same advancements weren't used in .45 bullets?

The .45 is still better. The 9mm is just good (lethal) enough now that the increase in capacity outweighs it.

jbp-ohio wrote: ↑Sat Jul 04, 2026 6:42 pm The argument is always, ''Advancements in bullet technology makes the 9mm equal to the .45 now.'' Those same advancements weren't used in .45 bullets?

Somewhat. My perception is that the major science got thrown at answering the 9mm's performance issues (which were mainly a matter of too much expansion and not enough mass to give adequate penetration). The bullet design advancements from that got spackled onto the .45, certainly, but I'm not sure to what degree they were applied SPECIFICALLY to the .45's performance envelope.

The FBI laid down 12"-18" penetration figure for a pretty simple reason - on a side shot into the upper arm of a large man, 12" will make it to the middle of the chest cavity, and 18" will make it to the opposite chest wall. Generally the 147 grain 9mm's I'm most familiar with open up to about .70" caliber and are better at making it to the deeper half of that penetration range, where the 230 grain .45's blow out into .90-ish caliber "parachutes" and tend to stop closer to the middle.

If I were running the show, we'd dial the expansion of the .45's down a little to bring the penetration up on par with the 9mm's. That's probably going to result in about an .80" caliber expansion for the .45 versus about .70" caliber for the 9mm. We could ponder on the advantages of that tenth of an inch in diameter all day, but the extra 2-3 inches in penetration DEPTH give a better chance of the bullet transecting something vital than the extra 0.2"-ish of extra diameter the original .45 HP brings to the party. What we would have done with my design tweak is create two wound tracks that are identical in all respects except for that 0.10" of diameter. Probably not much difference in performance to get excited about. Comparing the unaltered "fat" .45 that penetrates adequately, but not quite as much? Again, probably not sufficient change in performance to get excited about. The very slightly wider diameter might wreck the things it hits to a larger degree, but the deeper penetrator stands a greater chance of wrecking a larger number of things, and has more certainty of making it to the things it was aimed at in the first place.

jbp-ohio wrote: ↑Sat Jul 04, 2026 6:42 pmThe .45 is still better. The 9mm is just good (lethal) enough now that the increase in capacity outweighs it.

By what metric do we choose to define "better"? On a single bullet to single bullet comparison, the two are very close, and "better" comes down to how you want to massage diameter vs. penetration. I'd call 'em pretty much equal if it really was a 1-1 comparison - but it isn't. The thing that's driving the current popularity of the 9mm is not only the mag capacity, but also the lower recoil allowing the ability to make two holes in the time it takes Mr. Big Bore to make a roughly equivalent one. Even on platforms of equal capacity, the argument in favor of 9x19 is a pretty solid one.

From my experience shooting fat Missouri deer with .44 240gr JHP and never once recovering a slug i know lower velocity and larger slug would be more effective. The energy dissipated in the target is energy in - energy out. So the endless debate of lower velocity higher mass 45 compared to higher velocity lower mass 9mm seems endless and pointless. One thing i wouldnt want is over penetration of a defensive round critically injuring someone other than an intended aggressor. That tips the equation to 45 in my book

Japhy wrote: ↑Fri Jul 10, 2026 4:21 am From my experience shooting fat Missouri deer with .44 240gr JHP and never once recovering a slug i know lower velocity and larger slug would be more effective. The energy dissipated in the target is energy in - energy out. So the endless debate of lower velocity higher mass 45 compared to higher velocity lower mass 9mm seems endless and pointless. One thing i wouldnt want is over penetration of a defensive round critically injuring someone other than an intended aggressor. That tips the equation to 45 in my book

The key thing here is that we're now looking at lower velocity, higher mass 9mm's - at least for those using the 147 grainers. There are a lot of 124's still being used in official and unofficial capacity, but I'm not really a fan of 'em. When I looked at the test data for the various barriers the bullet has to go through before it gets to the gel block, the 147's were more consistent in penetration; the 124's were more likely to throw you a "deep here, but shallow there" result. The comparison of heavy 9mm to heavy .45 is probably similar to a heavy 160 grain 6.5x55 Swede vs. maybe a 165 or 180 grain .30-06. You can effectively hunt moose with either, but it's the higher sectional density of the 6.5 that allows it to penetrate and punch above its weight class. The heavy 9mm's are - sort of - playing in that ball park.

The amount of penetration achieved is more of a bullet engineering question than one of caliber, mass, or speed. ANY of the FMJ solids in the calibers we're discussing will penetrate double or more that what is asked for in the FBI protocol. The trick then becomes one of designing the hollowpoint to "parachute" the bullet to a halt at the depth you want. This is why I say there's little to choose between the calibers on a single shot to single shot basis - - they're all engineered to penetrate about the same depth, and all expand to within a couple tenths of an inch of each other. As to "energy", your target doesn't feel any more difference in impact between them than you do in recoil (thanks Isaac Newton). Foot-pounds really aren't a factor.

As to over-penetration. . . It was mostly UNDER-penetration that led to the development of the handgun bullets we have today. This is where we step away from the gel blocks and look at the real human target. Skin is a very tough and elastic medium. Very often, so is clothing. It is very common for our modern "magic" bullets to expend all their energy in transecting the torso and be brought to a halt on the exit side hide, thanks to their now expanded, blunt profile. A deep-diving bullet that makes it all the way to the FBI's maximum "ideal" depth of 18" on a gel block should have what it takes to penetrate an upper arm on a side shot and get all the way across to the far side of a torso, but thanks to the bouncy nature of skin and clothing, even on a frontal shot, that same bullet stands a good chance of being halted on the way out. At the very least, it won't have much gas left in its tank. All of that said, we collectively and historically miss a lot more than we collectively and historically hit (red dot sights seem to be helping with this, but it's still a bit early to tell for sure) - I'm more concerned about the misses that are free to roam than I am about the hits that are at least partially constrained by the intended target.

Soooo. . .you can massage a bullet for just about any caliber and speed combination to penetrate to a desired depth. Since everybody's using the FBI protocol to set that depth, the holes are about the same. That being the conventional wisdom, the 9mm lets you make more of those nearly identical holes faster, and for those who drink the capacity Kool-Aid, there's the psychological bump of carrying more of them. I'm just happy not to have to repair the G.D. .40's anymore.

An interesting take and nearly sound physics. But the kinetic energy = 1/2 mass X (velocity squared). If the bullet is stopped in the target all of the energy is dissipated in the target. If the bullet traverses through the energy dissipated in the target is the entry energy - the exit energy. The momentum is not all absorbed in the target if the bullet passes through. Momentum is the integral of kinetic energy by time. exit energy matters a lot
Im sticking with a 4 1/4 inch Springfield Ronin and 230 gr 45 ACP JHP, factory irons ie no battery failures, no sheared mounting bolts, no gawking high and low to find the dot.

If you’re gawking high and low to find the dot, you re untrained or simply retarded.

I know the 45 is Gods caliber, and most carry a .45 cause they don’t make a .46.


But I’ll take a 9mm with twice the capacity, less weight, smaller easier to conceal package, easier shooting, and the accuracy of a red dot. And if the dot happens to shear off (it really can’t with a properly machined slide) I’ll just use the backup sights.

Ahhhh…….where to start.

Eh, nobody will listen anyway. We all have our preconceived notions of past history and rhetoric. Oh, and don’t forget numbers!

Red dots.
When you have good eyes…..I would say they are not necessary. But, with training and practice, they are more accurate and possibly more accurate.
When you have old eyes………..I just spent a week of intensive pistol training with an iron sighted G43X and a RDO mounted G47. At close range, mostly a wash on speed. RDO was more accurate. At distance of 15-25y, RDO all the way for speed and accuracy. I simply couldn’t see the front sight on the 43x with any greater accuracy than a colored blur. But, the RDO was crisp and precise at any distance.

Yes, you have a training curve. If you aren’t willing to put the time and effort into them, don’t bother. But, if you are willing, my battery lasts more than a year with a quality battery constantly on and if it did die, I have backup irons.