Why is the 9mm a higher velocity round than the .38? With the smaller casing I would guess less powder for propellant would actually make it slower. Because the .38 is less powerful would that make it better for personal protection? Does it have a better chance of stopping on impact than passing through the intended target as the the 9mm might do?
Thanks.

I don't really know, but as to the question about which is the better "stopper" the debate rages on. IMHO pick the platform (revolver or semi auto) that works best for you (it's all about shot placement), practice, use a good SD round, and hope you never have to find out.

MY EDC is a S&W 442 or a Colt Cobra. My orbits in retirement from law enforcement are tame and I feel well armed for whatever may come my way.

Choose wisely and make sure you are up on local CCW law.

Best,
Old Cop

One reason is that a revolver has the cylinder gap between the bbl for gas to escape, reducing velocity somewhat. Also the .38 usually has a heavier bullet, when similar bullet weights are used it closes the velocity gap a bit between the .38 and 9mm. I doubt that there is any significant in penetration using similar weight bullets in the 2 rounds, Id feel well armed in my home with either cartridge, however the 9 will give you more rounds at hand than the .38 but for home defense I dont think youd use all the rounds the 9mm would offer over the .38.

Size of the case has nothing to do with it. The 9mm round has a much higher maximum pressure, where as the 38 Special is a low pressure round.

It's basically a marketing ploy. Although these are both very old cartridges, the ammo companies like to cling to the perception that the .38 Special is only as strong as 100 year old steel that was used to manufacture the original revolvers. But while the .38 Special does have far greater case capacity, the thin cylinder walls of even the modern K Frame .38 Special revolver tends to be the weak link that limits the performance.

The less powerful cartridge is best for personal protection? When the other guy has a gun and is pointing it at you the last thing on your mind will be whether you can "stop" him in the most efficient manner possible without hurting him too much. Handguns need all the stopping power they can get, and it's a good idea to use as much bullet weight and velocity as you can manage. That said, there isn't a whole lot of difference between the 9mm and .38 Special.

Dave Sinko

Actual case capacity has nothing to do with it. The 9mm was designed with the case capacity it needed -- for smokeless powder --to fit new firearms. The 38 special was designed -- for black powder -- to allow an improvement over an old cartridge (.38 colt) to allow a new revolver to be able to use both cartridges but the old revolver not use the new.

The 38/44 showed that the .38 special had the "room" to make "magnum" power but, again, it was lengthened to the .357 case -- not to have more room inside but to make the outside not fit in older revolvers.

To me this has been one disadvantage of revolver vs semi design. When a semi-round can be improved -- a new cartridge and chambering is developed usually meaning more power in smaller space. A new round in a revolver means a longer cylinder.

Thanks for the education gentlemen.

Huh? The 38 Special is not a "marketing ploy". It is a standardized cartridge with a defined pressure limit. Ammunition manufacturers can't just ignore that pressure limit and make souped up 38 Special loads, for safety and liability reasons and just general common sense. Even the small increase in pressure for +P had to be defined and standardized.

Thin cylinder walls on modern K-frames? Which guns are you referring to? Because the most recent 38 K-frames that S&W produced were some of the strongest 38 Special revolvers ever made. These guns are not the "weak link".

Dont make simple things complicated. The 9mm is loaded to higher pressure, and pressure is what makes the bullet go.

9mm 35,000 PSI
9mm+P 38,500 PSI

.38 Spl 17,000 PSI
.38 Spl +P 20,000 Psi

.357 Mag 35,000 PSI

It's not the extra 1/8" on the case that makes the .357 faster than a .38SPL, it's the jump from 17,000PSI to 35,000PSI.

__________________
Science plus Art

And the .38spl case can be loaded to near 357 mag power if you fire it in a 357 mag. There is very little difference in potential between them with the limiting factor being the cylinder strength.

One case in point would be the Model Tens chambered for 357 Magnum. Weak? Hardly. I subject my M-64 to a constant diet of 38+P loads, and it couldn't care less. My previous duty gun was a Model Ten made in the early 60's, and over 5 years I poured nearly 70,000 rounds of hot 38 ammo through it in my quest to extinct the local Bowling Pin population. The gun never failed me.

The .38 is about 18,500 psi and the 9 is somewhere around 27,00psi I believe. The .38 case size is something left over from the black powder days of 1898. Check that 9 psi please.....The .357 runs around 35,000 psi. The 9 was invented around smokeless powder hense the smaller case.

What we're looking to achieve is a way to propel the largest mass at the greatest velocity possible. Pressure is a component of propulsion.

The pressure data shows the required force within the volume of a given cartridge in order to achieve a desired velocity. It is a limiting factor for choosing the vessel.

Look at data for like weight bullets and you will see that the .38 Special round achieves a similar velocity at a lower pressure than that required for the 9 mm Luger. This follows Boyles Law (P = 1/V) due to the higher volume of the .38 Special cartridge.

Additionally, the greater volume of the .38 Special cartridge allows for a larger mass to be propelled than that of the 9 mm.

...Maybe...

A Model 10 .357 Magnum is NOT the same as a Model 10 .38 Special. Everybody knows that the K Frame can handle the .357 Magnum cartridge. They just tend to be chambered for .357 Magnum and not .38 Special.

My Model 64s will shoot and extract so-called factory loaded +P+ all day long. What does that tell me? Now that the factories have hyped the +P and +P+ designations for all they're worth, maybe now they can introduce +P++ and charge you even more for a questionable gain in velocity. Anybody who handloads .38 Special will realize that a Model 64 can not handle the same loads and pressures that even a J Frame Model 60 can handle, and it's because the cylinder walls and position of the stop notches over the chambers are the weak link in the K Frame .38 Special platform.

There is too much variation across the spectrum of 9mm and .38 Special revolvers and semiautomatic pistols to have any kind of meaningful discussion of "9mm vs. .38".

Dave Sinko

Any personal defense load I use, whether in my 9mm or 38 special will be +p with a gold dot bullet. The type of bullet for the intended purpose is critical.

The 9mm parabellum is designed for higher pressure than 38 special, and typically uses a lighter bullet (124 v 158 grain), which combine to provide higher velocity. Since energy is proportional to the square of velocity, the 9mm also delivers about twice the muzzle energy.

The relationship between pressure and case capacity, powder volume and performance is complicated. The same load in a smaller case usually results in higher pressure. A larger load in the same case usually results in higher pressure (but not always). Faster burning powders result in higher peak pressure, but often lower velocity than larger volumes of slower powder. If you load black powder into a musket and push the ball halfway down the barrel, rather than snugly on top of the powder, you get a 36" pipe bomb.

In a nutshell, that's why we have SAAMI standards, pressure gauges and, more important, loading tables.

Peak pressure is only one component of power, the other is the duration the pressure is sustained. Area under the curve.

and yet there are people out there that have rechambered the J and K frame 38's to 9mm moon clips, with no ill affects

I always wondered about this. Surely a 9mm is hotter than a .38, why is this no problem? I would think it would be, if you look at the pressure levels.

I bet the ill affects would show up after extended shooting.

From what I have read and experienced, K frame revolvers in 357 Magnum are prone to having the forcing cone split from lots of high pressure 357's, especially 125 grain ammo. I do not think that cylinder strength is a limiting factor.

I'm not sure of the point you are trying to make about ammo manufacturers "hyping" +P or ++P ammo.

Either way I would not chose to stand in front of either.

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NRA Bene Life, SWCA 2372