Caliber question: Help me understand this.

[FireInCairo]

Ok, so why is the 9mm considered to be a better self defense round over a .38 special +P?

If I compare the two cartridges, the .38 special looks a lot bigger compared to the 9mm cartridge.

What am I missing here? I'm a newb, so please help me understand.

 

[murf]

pressure. the 9mm +p is rated at 38,500 psi, the 38 special +p at 18,500 psi.

the 9mm goes faster.

murf

 

[Skribs]

http://en.wikipedia.org/wiki/.38_special#Performance

.38 SPC +P+ looks to have about 75% the muzzle energy of a 9mm. Size isn't everything.

 

[X-Rap]

Though not alwys true, the 9mm pistol of similar size typically holds at least twice the ammo capacity. Combine that with the superior balistics and it's hard not to like.

 

[grendelbane]

To be fair to the .38 Special, for most of its life, it was actually considered the superior cartridge. (At least in English speaking countries).

In the early years of the XXth century, the .38 Special was loaded with lead bullets, while the 9mm was loaded with full metal jacket bullets.

Around 1930 Smith & Wesson offered its .38-44 revolvers, which used the same bullet, but at a much higher velocity. These were supposed to be shot in large frame revolvers.

About the dawn of the age of Aquarius, jacketed hollow point bullets became popular in both cartridges. The 9mm, with its higher pressure now does better. Lots of old, weak .38 Special revolvers out there now, so the manufacturers don't load it to higher pressures.

The 2 cartridges are of a similar age, and it is really only in the last 40 years that the 9mm has come to be considered the superior cartridge.

The popularity of semi auto pistols also helped to make the reputation of the 9mm, as the revolver lost its popularity in many circles.

 

[FireInCairo]

Now I see. Thanks for the information. I learned a lot. I will use the 9mm with confidence now.

 

[Manco]

If I compare the two cartridges, the .38 special looks a lot bigger compared to the 9mm cartridge.

By the way, one of the reasons for the difference in case size is that .38 Special started out as a black powder cartridge, which is less efficient in terms of energy per volume. Subsequent smokeless powder .38 Special loads have to remain compatible with the specs, which typically leaves most of the case empty. Physically, you could load .38 Special cartridges a lot hotter than 9mm cartridges if you wanted to, but then they wouldn't be .38 Special anymore (they'd be closer to .357 Magnum, and such loads could be fired in .357 Magnum revolvers).

For comparison, 9mm was designed for smokeless powder, and has been pretty much maxed out from the beginning (slightly more powerful +P loads notwithstanding). It's more efficient in terms of cartridge size for the reasons given above, so it has some advantages (although .38 Special is still an extremely popular and viable cartridge today, of course).

 

[BCRider]

Note that the OP mentioned +P and not regular .38Spl. That changes the picture a lot.

To get a fair comparison let's look at 124/125gn bullets and 147/146gn bullets for velocity. I'm using the Hodgdon reloading data for my reference.

Top speeds for max loads in the 124gn 9mm vs 125gn +P are around 1100 and 1080 fps respectively. That's all close enough to call it a wash.

For the heavier 147 in 9mm vs 146 gn out of the .38+P we've got around 880 for the 9mm vs 920 for the .38+P.

These speeds are my eyeball average of all the top speeds for the range of bullets of that weight. Actually doing the math might change it by a little. But I suspect it would still all result in the results being within "spittin' distance" of what I've posted.

The peak pressure may be higher for the 9mm but it's muzzle speed and bullet weight that counts for comparing. And from where I'm sitting they look close enough to call it a wash.

 

[Lawdawg45]

BCRider nailed it. Also, the comparison between standard 9mm SD rounds and .38 +p aren't so dramatic, and considering that most of the micro-pocket 9mm's can't handle the +P's, the .38+P is still the winner in pocket pistols.

LD

 

[FireInCairo]

By the way, one of the reasons for the difference in case size is that .38 Special started out as a black powder cartridge, which is less efficient in terms of energy per volume. Subsequent smokeless powder .38 Special loads have to remain compatible with the specs, which typically leaves most of the case empty. Physically, you could load .38 Special cartridges a lot hotter than 9mm cartridges if you wanted to, but then they wouldn't be .38 Special anymore (they'd be closer to .357 Magnum, and such loads could be fired in .357 Magnum revolvers).

For comparison, 9mm was designed for smokeless powder, and has been pretty much maxed out from the beginning (slightly more powerful +P loads notwithstanding). It's more efficient in terms of cartridge size for the reasons given above, so it has some advantages (although .38 Special is still an extremely popular and viable cartridge today, of course).

he he I was actually coming back today to ask why the cartridge in a.38 is bigger.