Explain equal SAAMI limits but different ballistics for .357 Mag and 9mm

[rpenmanparker]

Here's another comparison to help illustrate the issue of how case capacity influences pressure and velocity.

The 357 magnum has a very long case and overall length and with a pressure limit of 35,000 psi will push a 125 grain bullet to 1450 fps from a 4" (vented i.e. revolver) barrel.

You can get the same ballistics from a semi-auto cartridge, but at a higher pressure because they have less space. For example, the 9X23 Winchester has a much shorter case and overall length. It also pushes a 125 grain bullet to 1450 fps (matching the 357 magnum), though in a 5" barrel. But it's pressure limit is 55,000 psi, much higher than the 357 magnum.

The bottom line is that case capacity matters and determines what type of performance you can produce at a given pressure

I get that now. Never considered case length for that aspect of performance before.

 

[jmr40]

Barrel length.

The better 124 gr 9mm loadings from a 5" barrel will match 125 gr 357 mag speeds from 4" barrels. And the 9mm pistol will have a shorter overall length. All of the published 357 mag data is from 8" test barrels. When shot from real guns with realistic barrel lengths neither 357 nor 44 mag look nearly as good as they do on paper.

 

[rpenmanparker]

Barrel length.

The better 124 gr 9mm loadings from a 5" barrel will match 125 gr 357 mag speeds from 4" barrels. And the 9mm pistol will have a shorter overall length. All of the published 357 mag data is from 8" test barrels. When shot from real guns with realistic barrel lengths neither 357 nor 44 mag look nearly as good as they do on paper.

No doubt, but it is still true that they buck like a bronco. .357 is the introductory cartridge at the school for unpleasant shooting. Why this is true at the same top pressure as 9mm I just don’t know...but it is.

 

[MEHavey]

357 is the introductory cartridge at the school for unpleasant shooting. Why this is true at the same top pressure as 9mm I just don’t know...

Because pressure is (relatively) irrelevant to recoil unpleasantness using the same weight bullet.
It's the (delta-V)squared coming out of the muzzle.
( and . . . the 357 can be firing a significantly heavier bullet as well)


.

 

[fxvr5]

The better 124 gr 9mm loadings from a 5" barrel will match 125 gr 357 mag speeds from 4" barrels. And the 9mm pistol will have a shorter overall length. All of the published 357 mag data is from 8" test barrels. When shot from real guns with realistic barrel lengths neither 357 nor 44 mag look nearly as good as they do on paper.

There's a lot of BS there.

I don't know where you're getting your 9mm data from. Even the hottest +P+ 9mm ammo falls short of 357 magnum performance.

https://www.buffalobore.com/index.php?l=product_detail&p=119


BTW, The ballistics of 357 magnum ammo, such as the 125 grain bullet at 1450 fps, is from a 4" vented barrel.

https://images.remington-catalog.com/5689a6e8f1985
https://cdn-federalpremium2.azureed...emium_catalog_2018.pdf?v=1&d=20180506T022358Z

I've shot the Remington 125 SJHP from a 4" S&W 686, and it clocked a few fps over 1450 fps.

And heavy 357 ammo (gunpowder selection is important) pushes it even faster from a 4" barrel.

https://www.buffalobore.com/index.php?l=product_detail&p=103

 

[mavracer]

Barrel length.

The better 124 gr 9mm loadings from a 5" barrel will match 125 gr 357 mag speeds from 4" barrels. And the 9mm pistol will have a shorter overall length. All of the published 357 mag data is from 8" test barrels. When shot from real guns with realistic barrel lengths neither 357 nor 44 mag look nearly as good as they do on paper.

No they don't, not really, no they don't, and whatever.
No matter how many times you post this BS it's not true.
Remington UMC 125gr jhp lists 1450 from a 4" vented barrel and my cronograph confirms that

 

[fxvr5]

No doubt, but it is still true that they buck like a bronco. .357 is the introductory cartridge at the school for unpleasant shooting. Why this is true at the same top pressure as 9mm I just don’t know...but it is.

First, jmr40's post was full of BS. A 9mm feels much milder than a 357 Magnum because it is much milder.

Second, when you compare two real cartridges like the 9X23 Winchester and 357 Magnum that push the same bullet to the same speed, you have to look at how they do that. One of the more common ways the 357 Magnum pushes 125 grain bullets to 1450 fps is to use a large amount of slow powder, like Winchester 296. Charge weights can run up to 21-22 grains. This powder also produces wonderful fireballs that add to the noise and spectacle of the muzzle blast. But the cases are pretty full at this weight. That much powder takes up a lot of space.

The 9X23 Winchester's smaller case can't use 296 very well, so it has to use somewhat faster powders that are more efficient, but at the same time produces higher pressure than the 357 Magnum does. Still, factory 9X23 ammo uses about 10 grains of powder, based on the ones I've pulled and measured. The 9X23 has plenty of recoil in it's own right, because there is no free lunch. But the lesser powder charge, and that fact that it is in a semi-auto pistol, makes it feel like less than the 357 magnum in a revolver.

The gunpowder, and how much gunpowder is required to get the same velocity, matters. If you compare gunpowders that use different amounts to push the same bullet to the same speed, the one that requires more weight produces more recoil. That's because the weight of the gunpowder is part of the ejecta that comes out of the barrel, and that increases recoil force. This is well known, and formulas that calculate recoil require the weight of the gunpowder.
https://en.wikipedia.org/wiki/Recoil#Including_the_ejected_gas
http://kwk.us/recoil.html

I hope this helps you to understand some of the differences between cartridges and recoil.

And if you want to get an even better understanding of how important powder selection can be in high performance, check out the link below. It is possible, when selecting the right powder, components, and overall length, for a 38 Super to match the ballistics of the 9X23 Winchester and 357 Magnum with a 124/5 grain bullet, and still stay within the 38 Super's normal pressure limits. http://www.shootingtimes.com/editorial/super-powders-for-the-38-super/99160

For another explanation of how gunpowder contributes to recoil, see this article: http://www.shootingtimes.com/editorial/gunpowder-contribution-to-recoil/328788

 

[rpenmanparker]

First, jmr40's post was full of BS. A 9mm feels much milder than a 357 Magnum because it is much milder.

Second, when you compare two real cartridges like the 9X23 Winchester and 357 Magnum that push the same bullet to the same speed, you have to look at how they do that. One of the more common ways the 357 Magnum pushes 125 grain bullets to 1450 fps is to use a large amount of slow powder, like Winchester 296. Charge weights can run up to 21-22 grains. This powder also produces wonderful fireballs that add to the noise and spectacle of the muzzle blast. But the cases are pretty full at this weight. That much powder takes up a lot of space.

The 9X23 Winchester's smaller case can't use 296 very well, so it has to use somewhat faster powders that are more efficient, but at the same time produces higher pressure than the 357 Magnum does. Still, factory 9X23 ammo uses about 10 grains of powder, based on the ones I've pulled and measured. The 9X23 has plenty of recoil in it's own right, because there is no free lunch. But the lesser powder charge, and that fact that it is in a semi-auto pistol, makes it feel like less than the 357 magnum in a revolver.

The gunpowder, and how much gunpowder is required to get the same velocity, matters. If you compare gunpowders that use different amounts to push the same bullet to the same speed, the one that requires more weight produces more recoil. That's because the weight of the gunpowder is part of the ejecta that comes out of the barrel, and that increases recoil force. This is well known, and formulas that calculate recoil require the weight of the gunpowder.
https://en.wikipedia.org/wiki/Recoil#Including_the_ejected_gas
http://kwk.us/recoil.html

I hope this helps you to understand some of the differences between cartridges and recoil.

And if you want to get an even better understanding of how important powder selection can be in high performance, check out the link below. It is possible, when selecting the right powder, components, and overall length, for a 38 Super to match the ballistics of the 9X23 Winchester and 357 Magnum with a 124/5 grain bullet, and still stay within the 38 Super's normal pressure limits. http://www.shootingtimes.com/editorial/super-powders-for-the-38-super/99160

For another explanation of how gunpowder contributes to recoil, see this article: http://www.shootingtimes.com/editorial/gunpowder-contribution-to-recoil/328788

Now this is a valuable reply! Thanks.

 

[Texas10mm]

No they don't, not really, no they don't, and whatever.
No matter how many times you post this BS it's not true.
Remington UMC 125gr jhp lists 1450 from a 4" vented barrel and my cronograph confirms that

I too was wondering where he got that idea. Most .357 mag 125 gr loads are in the 1300-1400 fps territory and 124/125 9mm is in the 1000-1100 fps territory.

 

[Toprudder]

.... This is why a 9mm in a 16" barrel will see around 1-200 FPS increase, while a 357 can easily see a 4-500fps increase. That extra volume really shines in a longer barrel, the same reason why .357 loads are usually tested in them. A 9mm uses fast to slow pistol powders, which are denser. A typical 9mm load fills the case to the bullet base, and will be pushed down when the bullet is put in. You can get a slight increase in velocity from a pressure gain, and it takes only a very small amount of extra powder .2-.5 grains to reach +P levels. Plus P gains are usually not that great, and factory +P is usually hotter due to the greater accuracy of testing in a factory setting allowing a manufacturer to push limits to SAAMI max.

A lot of truth to what you say.

The most gain I saw in 9mm, going from a 4.7" to a 16" barrel, was 250fps. The most I saw with 357, going from a 5" to a 16" barrel, was 600fps.

Interestingly, the 357mag tests I did was with 300-MP powder and 158gn XTP/FP bullets. In my 5" revolver, the velocity peaked at a charge of only 16.1gn of powder. Increasing the charge all the way up to 17.0gn, (max published is 18.6) saw no increase whatsoever. However, when I tested in the 16" barrel, I saw a linear increase in velocity all the way up to the max, slightly over 1800fps. Comparing more apples-apples, with 16.1gn charge in each barrel, it was 1200 vs 1580, still almost 400fps. But the longer barrel definitely took more advantage of the slow burning powder.

Also interesting is that the load data Alliant publishes for 300-MP is shot from a 10" barrel.

 

[jmorris]

Even the hottest +P+ 9mm ammo

FWIW there is no SAAMI pressure limit on +P+ 9mm that just means it’s over +P pressure, all the way to kaboom is +P+.

The load you linked to won’t even make major PF and there are lots of folks that load major 9mm.

 

[fxvr5]

FWIW there is no SAAMI pressure limit on +P+ 9mm that just means it’s over +P pressure, all the way to kaboom is +P+.

The load you linked to won’t even make major PF and there are lots of folks that load major 9mm.

Correct on both points. SAAMI has a pressure limit for 9mm +P at 38,500 psi. +P+ is God only knows.

You're also correct that the Buffalo Bore won't make major power factor. It screams for a 9mm, but, as you note, competitors that load 9 Major push the bullets even faster. I load 9 Major, and some of those loads are scary in how far those charge weights exceed published load data. For people curious about 9 Major, here's an article with some information; https://www.ssusa.org/articles/2018/1/9/how-to-use-9-major-in-a-short-barrel/

But 9 Major also requires the correct barrel design and gun to handle the pressure, so readers should not think you can load it for just any old 9mm caliber gun. Many guns can't handle it and the results are bad for the gun and extremely dangerous for the shooter. Guns are often purpose built for this cartridge. Pressure with some powders are likely in the 50,000 psi or higher range. Many loaders use the slowest powder they can to help keep pressures low, and slow powders generally require large charge weights, and this aids in gas pressure for the compensator.

I tried some 'factory' loaded 9 Major ammo, and one of the 124 grain loads was scary fast at 1498 fps from a 4.6" barrel (185 power factor). Yikes!

 

[Toprudder]

But 9 Major also requires the correct barrel design and gun to handle the pressure, so readers should not think you can load it for just any old 9mm caliber gun.

This made me think about 38 super. 38 Super is basically just a longer 9mm case. I have often wondered if 9mm couldn't be loaded with a 38 super COL, with a barrel cut with a longer leade, and get 38 super performance. I would be surprised if no one has done this. The only issue I can think of is neck tension, with less of the bullet in the case. 9mm pressure is 35k, 38 super is 36.5k, which is less than 9mm +P but equal to 9mm NATO.

 

[fxvr5]

This made me think about 38 super. 38 Super is basically just a longer 9mm case. I have often wondered if 9mm couldn't be loaded with a 38 super COL, with a barrel cut with a longer leade, and get 38 super performance. I would be surprised if no one has done this. The only issue I can think of is neck tension, with less of the bullet in the case. 9mm pressure is 35k, 38 super is 36.5k, which is less than 9mm +P but equal to 9mm NATO.

In a word, yes. Folks who run 9 Major in a 1911 will often load longer because the 1911 magazine will accept a longer cartridge like the 38 Super. It depends on if they're using spacer in the magazine, and what the spacers will allow. It's all about case capacity and loading longer increases case capacity and can reduce pressure. As noted, then the constraint is how much of the bullet is still in the case. Some 9 Major shooters on the Brian Enos website have had issues will bullets falling out of their case during feeding for this reason (the problematic bullets are the 115 grain bullets because they're shorter than heavier bullets), so they've had to balance their loads with a practical overall length for these bullets.

In the article in posted above, the rounds had to fit in a Glock magazine which limits their overall length to what will fit in the magazine. But as long as the long loaded rounds will fit in the chamber (with a long throat), you can load as long as the magazine will take.

EDITed to add: some of the IPSC/USPSA shooters who used the 9X21 (when the 9X19 was banned) loaded their rounds to 38 Super length for the reasons above.
http://www.k8nd.com/documents/hl9x21.pdf

 

[Texas10mm]

This made me think about 38 super. 38 Super is basically just a longer 9mm case. I have often wondered if 9mm couldn't be loaded with a 38 super COL, with a barrel cut with a longer leade, and get 38 super performance. I would be surprised if no one has done this. The only issue I can think of is neck tension, with less of the bullet in the case. 9mm pressure is 35k, 38 super is 36.5k, which is less than 9mm +P but equal to 9mm NATO.

I don't think you would have enough neck tension to keep the bullet from getting knocked out of the case during chambering.

 

[rfwobbly]

... like Winchester 296. Charge weights can run up to 21-22 grains. This powder also produces wonderful fireballs that add to the noise and spectacle of the muzzle blast.

...and nice sun tans...