superdude

Was this from a rest (bench)?

The twist rate is different (though optional), but the groove diameter specs are the same. The groove diameter being the same is what people go nuts over.

You're really overthinking this. The .004 DOES apply to the groove diameter.

There is no such thing as a 38/357 barrel and a separate 9mm barrel. They both have the exact same specs. If you buy a 38/357 revolver and the barrel groove diameter measures .355", does that mean it has a 9mm barrel? No, it doesn't. That's because .355 is within the SAAMI specs for a 38/357 barrel. It's still a 38/357 barrel.

Ah. You're reading the SAAMI specs for the pressure test barrel (Page 141), which is used for measuring chamber pressure. The specs for the 9mm cartridge and ammo are on page 27, and for the 38 Spl. are on page 47.

Ammo manufacturers are making their 38/357 bullets according to SAAMI specs for that caliber. You can load 9mm bullets in 38/357 cases, but the cases (and our reloading dies) are designed to fit the presumed .357ish bullets, and smaller bullets will have less, or no neck tension. You can get around it by using an undersize sizing die, if you want. I've done it, and other people have, too. Accuracy with jacketed bullets is fine. Lead might be a different issue and I have not tested that. You can also use .357/.358 bullets in your 9mm. The issue here is whether they will fit in the chamber, since the brass and chambers are made around SAAMI specs and a 'tight' chamber might not like a .357/.358 bullet. But, lots of us use these bullets in our 9mm guns without issue. SAAMI barrel tolerances are +.004, not .0004, so a barrel with a groove diameter from .355 to .359 is within specs. Colt is known for making some of their revolver barrels undersize. I have a Colt Magnum Carry with a .3532" groove diameter. I've not had any issues with the ammo I've fired through it.

These ammo standards were established long before most of us were born. The 9mm and 38 Special were created around 1900, give or take. At some point in the past someone decided that such-and-such was going to be dimension X, and that other thingy would be dimension Y. We're left to sort stuff out. But SAAMI is the bible in the USA, and CIP is the bible for the rest of the world. They define the standards, and companies build their products around them.

I don't know where Brownells is getting their information, but it is not consistent with SAAMI. SAAMI is the industry standards institute, not Brownells. The bullets are different because their dimensions are also defined by SAAMI (and tradition). See the information in the Link I posted. 9mm bullets = .3555 - .003. 38/357 = jacketed = .3580 -.003; lead = .3590-.003 I've slugged many 9mm and 38/357 barrels and don't find a difference between them. Of the over a dozen 9mm barrels I've slugged, only 2 of them were less than .356".

9mm and 38/357 have the exact same SAAMI barrel specs: groove diameter of 0.355" + 0.004". So any barrel with a groove diameter between 0.355" to 0.359" is within spec for both calibers. https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.3-CFP-and-R-Approved-2015-12-14-Posting-Copy.pdf

The funny part is that the Remington ammo catalog shows the primer used in 40 S&W is the 1 1/2.

This table originated from the link below, and it has specific information about 9 Major in a short barrel. https://www.ssusa.org/articles/2018/1/9/how-to-use-9-major-in-a-short-barrel/

According to your numbers, you lengthened the OAL. This made the bullets faster?

Since you are not loading for competition where a consistent power factor is useful, you can ignore extreme spread and standard deviation. Testing has shown that there is no correlation between ES/SD and accuracy for the typical handgun at typical handgun distance. https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/ Serious accuracy testing is done at longer range and with a stable method. You can't tell much from a 5-shot, or even a 10-shot group unless the difference in accuracy is 4-fold plus. Group size will vary considerably even when shooting the exact same ammo. Even then you have to consider the method - offhand, bench, Ransom Rest. https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group/ https://www.ssusa.org/articles/2021/2/17/accuracy-testing-how-many-shots-in-the-group

As noted, you'll have to test your ammo. That said, my notes show with a 115 gr bullet in a 9mm using 5.0 Silhouette in a 5" barrel going from 1.160 to 1.120 (0.040" reduction OAL) power factor went up 6.

Some information here: https://www.ssusa.org/articles/2018/1/9/how-to-use-9-major-in-a-short-barrel/ Always work your loads up.

Popple holes work half-way like a compensator. With a compensator, gas hits the baffle plates and this pushes the compensator forward (and anything attached to the compensator). The gas is also directed upward through those big compensator ports, and this pushes the compensator down, reducing muzzle rise. With popple holes (barrel ports) the gas is directed upward and this pushes the barrel down, reducing muzzle rise - like a compensator. The holes also bleed off some of the gas pressure behind the bullets so they don't go as fast as they normally would. A slower powder, specifically a powder that requires more charge weight to produce the same speed as other powders, will increase gas pressure/volume, and this extra gas pressure/volume is what aids compensators and ports. More pressure blasting up means more pressure force pushing down.

You'll need more powder to make pf when you have popple holes / ports. They bleed off pressure as the bullet passes by, and the bullet won't be as fast as it would in a non-ported barrel.

Some of the Berry's RN bullets have long noses which allow them to be seated long even in barrels with short throats. But the plunk test is essential to determine what length will fit in your chamber, and you have to sort this out first. https://www.shootingtimes.com/editorial/reloading-tips-the-plunk-test/99389

Just an FYI on the 45 versus other calibers and compensators - compensators work on a 45. The only difference between the effectiveness on a 45 versus smaller calibers is the bullet weight. 45s use heavier bullets than smaller calibers. If the bullet weight is the same on the 45 and smaller calibers, and they use the same gunpowder to push the bullet to the same speed, the compensated 45 will have less muzzle rise than the smaller calibers - because the 45 uses more powder weight because of the larger case and bore. Tested 45 Auto and 38 Super: https://www.shootingtimes.com/editorial/compensated-45-vs-compensated-38/99515

Cool! I wasn't aware.

You'll be limited by what will fit in the magazine. Isn't the Czechmate based on 9mm-length magazines?

What is the perceived advantage of the 9X21? The 9mm and 9X21 have the same loaded maximum OAL, so the only difference between them is the length of the brass. They reach the same ballistics with the same pressure (when at the same OAL).

Page 1, paragraph 7 http://www.k8nd.com/documents/hl9x21.pdf Page 2, paragraph 1 http://www.k8nd.com/documents/hl38sup.pdf

My understanding is that rifle primers, which have thicker cup material, have been used to reduce primer flow from loads that were often exceeding normal pistol pressure limits. The pistol primers would sometimes have primer flow that could cause the primer to pierce or flow back into the firing pin hole and plug it up. This depends on the powder and the primer and the pressure. Many people find that pistol primers work fine with their load in their gun.

Yes. Not uncommon.