He also did a lot of work on bullet development. Here's a chapter on the Keith bullet design. I don't have the 452424 mould. The one I had the opportunity to pick up is the 452423. It's not as heavy as the nose is not as large. The 452432s drop out at 245 grains.
When Elmer was experimenting, all the .45 Colt guns were made of mild steel and designed for a low pressure black powder load. Now you can get T.C. Contender and Ruger pistols that will take a modern load. There is separate data for those handguns and a safe load for my Ruger would dangerously unsafe in an older pistol. I am working directly from published load data and starting at the lower end of the recommended loads.
Nosmo King made an important observation in his comment yesterday.
There's no substitute for a decent chronograph during load development because not only does it show absolute velocity, it will report velocity variances between rounds; velocity consistency (low Sd) is a hallmark of a good load.The next time I go to the range with this .45 Colt load I'm working on, I'll take the chonograph and report what I'm getting. Load data expects it to be about 1100 fps. The underlying reason it's important is that there is a relationship between velocity and pressure. Development work has been done for each powder and bullet weight and an extrapolation can be made about what maximum pressures are based on the chronograph results.
Consistent chronograph results mean I am making good quality rounds. If the bullet weight, sizing, powder charge and case crimp are repeated consistently, there will be a small standard deviation around the velocity average.
I expect good results based on my first outing. But I am standing on the shoulders of men with far more experience than me.