K-Texas

If you need more detail on finding the correct OACL for 9mm jacketed bullets, I did an article a few years back at: https://blog.westernpowders.com/

And Glock shortened their 9x19mm chambers starting with the Gen 5s. Except for a few brands like the Caniks and 1911s, short chambers are now the norm. CZ has probably been using short chambers longer than any other maker, S&W 3rd generation steel pistols and those that have come after. With HK & Walther you get short and stepped chambers. If you were using the RMR 124 gr. In-House JHP I'd tell you that you could just use data from SIERRA and Lyman who both load the SIERRA 125 gr. JHP to an OACL of 1.075". The bullet shanks are very similar in length, and therefore, the bearing surface. The easiest method for checking is to take a WIN FIRED case, just barely start the bullet into the case, then place the "dummy" in the chamber, then push lightly on the case rim until the case stops moving forward. For 147s with long shanks, that may or may not work. If it does, the barrel's throat/leade will seat the bullet at its Max Possible OACL. Shorten your handloads by .010" and you should be good-to-go. Something else that will help if the 147 appears to be getting seated completely is that the case rim will be about 1mm below the barrel's hood, and not beyond being flush with the hood, or the bullet is not being completely seated in the chamber-length test. I specified WIN cases because I find them to be about the most uniform at around .011" thick within 1mm of the case-mouth. If you happen to be using Starline, or a few other domestic brands they're fine except that the new Style R-P are thicker than the old style.

The only differences I've seen is that nickel cases, depending on brand, can be slightly thicker like .012" within 1mm of the case-mouth vs .011" for non-plated. As far as data, different makers of plated bullets have their own guidelines and velocity specs. They are typically .356" dia vs .355" for jacketed, so there's obviously a difference. Some makers say to use cast bullet data, while a few say jacketed data is okay. Maybe the best policy, depending on the powder/brand is to use plated data for bullets of the same dia. and usually .356" If you use Accurate or Ramshot powders, you'll find data for plated bullets as well.

Since it appears that you have a source for Western Powders, I would recommend AA No 2. Really surprised that it gets so little mention on this forum. It has the flexibility to load many cartridges very effectively from .38 Sp. to .45 ACP target loads. It is insensitive to powder positioning in the case like TiteGroup. It does not, however, create the very high flame temperatures of TiteGroup. I've been using No 2 with the RMR In-House 124 gr. JHP at 127 PF with a Standard Deviation of 5 FPS. If someone really thinks they need a softer shooting load, then obviously, it ain't recoil that hampers their accuracy. I'll also mention that since Hodgdon Clays is no longer available from the original exporter, ADI in Australia, Ramshot Competition has proven to be a worthy replacement.

Hodgdon'e responsible for the warning about using WST for 9mm. Amazing that there wouldn't be problems with Major loads in .40 S&W.

If the bullet is touching the lands upon ignition, it does raise pressure. How much will depend on the burn-rate of the powder with the faster burners having the higher increase.

The method is easier when you load .355" jacketed bullets. With oversized cast or plated you'll need to use your press. Get your OACL down to the point where with the round in the chamber, the case rim is flush with the barrel hood and then shorten in smaller increments like .005" or less. .005" is enough freebore provided your press can provide tight OACL variations. Not always easy to do with a progressive press. .010" of freebore is not so much to deter accuracy. Most pistol makers are using short chambers for 9 x 19mm these days. The XDm is certainly one of them. They allow for the use of 124 gr. 9mm NATO because of the "universal" long and slender bullet profile. Other bullet profiles like JHPs and truncated cone shapes with short ogives will require a shorter OACL. Something that might help are some cast or poly-coated bullets that the maker calls Round Nose that are something like a SWC in that the bullet diameter above the shoulder is smaller in diameter. Small enough to pass through the barrels throat without making contact with it. Here's a link to one example and I'm not sure you'll find one over 125 grains. https://www.snscasting.com/9mm-125-grain-round-nose-red-coated-1000ct/

2.9 grs of Ramshot Competition.

We say plunk test, but sometimes plunk & spin is more appropriate. When you drop those loads into the chamber and hear a plunk, you should also be able to rotate the round freely. Also remember that different bullet profiles require different OACLs.

Ramshot Competition, and recently I've been making loads with 4.2 grs of AA No 2 and the RMR 124 gr. In-House JHP.

Ramshot Competition, and I'm also looking into AA No 2.