Let me make some comments about some points that have come up above.

1. Modern powders are not necessarily the same as those in ye days of olde. Also, the instrumentation has become a whole lot better more recently. Piezo-electric strain gauges show pressure peaks the copper crusher system didn't. So, some load data has changed.

2. Even considering the above, published load data shows loads that were safe in their test guns or in test barrels in universal receivers. That doesn't mean they're either safe or dangerous in yours. It's wise to regard the max loads with great respect. One of the members of a defunct website made barrels for test purposes. They're made to exacting standards with minimum dimension bore, groove and chamber dimensions to provide a worst case scenario.

I developed long range rifle loads from data in one of the Sierra manuals. When a later version came out, I checked it to see if there were any changes. In the new book, my loads were out beyond maximum, yet showed only very mild pressure signs. A call to Sierra found that they had a new gun for test data. Apparently with a very different chamber & bore/groove. FWIW, after recently firing some 12 year old ammo, I found myself pulling down a couple of hundred rounds. Ended up changing powder. Not real sure what changed, maybe neck tension?

3. SAAMI protocol allowed whoever developed a cartridge to specify the test barrel length. Once chronographs became widely available, published factory velocities got much closer to real world figures. AFTER the customers realized just how much the claimed figures were distorted, SAAMI mandated handgun test barrel length that related to the guns being sold.

4. Trying to match velocities of boutique loaders is fraught with danger. First, they may have the bucks to get custom blended powders. You don't. Secondly, the phrase "meets SAAMI specs" poses a question. SAAMI has 3 pressure levels, a level production ammunition is supposed to voluntarily meet, a higher level that any sample from a given lot isn't supposed to exceed and then a level ammunition is NEVER supposed to exceed. Exactly which set of limits do they refer to? If they're doing small batch production with rigorous testing, they might be able to safely go with a higher level of pressure.

Having burned all that bandwidth, the May/June 2019 issue of American Handgunner has an article by John Taffin on 2400 in .38 Spl. He gives a load of 10 gr of 2300 under a Speer 18 GR LSWCHP. He also gives some load data for 155 gr and 170 gr cast bullets. I'd suggest you find the article online and note that the charges at the upper end are intended for use in N frame size guns.

HOLY NECROTHREAD! just noticed the OP date.