Let's talk about the process of load development, particularly competition loads.
This seems pretty straightforward if there are published data for a bullet roughly akin to what you plan to use (i.e. same weight and type, including lead data to use for coated) and if your gat accepts rounds loaded to max SAAMI OAL: You just load a couple different charges between min-max at a length at least the published OAL, chrono, test accuracy and felt recoil, and adjust based on those data until you find something that flips up your skirt when shot from your gun. Simple enough.
Unfortunately, many of the Most Glorious Competition Powders as loved by Doodie do not have published load data that meets the criteria above. Two examples:
- N320, a frequent darling, publishes no data for lead (the only lead bullet data they publish are for N330+.) N320 also has no data for bullet weights over 130 gr.
- WST, another that's oft-mentioned, publishes no data whatsoever for 9mm. Apparently Hornady 4e has a single set of numbers, but they pulled all of the data from subsequent editions because it's "not safe" in 9mm.
If you can figure out a starting point that doesn't explode in your face, this is fine and easy. Look for pressure signs, chrono it, work from there. Again, simple enough. But getting to that starting point with a given bullet weight is the issue.
Now, it is intuitively obvious that starting charge weights too high is an issue. But it is neither intuitively nor scientifically obvious that starting charge weights too low should be an issue, beyond the risk of not running the slide or having a squib. If you pay attention while you're testing, these are pretty easy to mitigate. And yet the Internet seems to think that OMG YOU CAN SPLODE YR FACE WITH LIGHT LOADS CUZ DETONATION despite the fact that this has never been reproduced in a lab.
In general, most people are idiots, and so if the choice is between "this phenomenon totally exists but has never been reproduced under controlled conditions" and "some derpface double-charged and blamed it on a dodgy physics explanation to save face", I would typically lean towards the latter. But at the same time, I also like to save my face.
So I guess my two main discussion questions are as follows.
One, is detonation with light charges actually a thing, or the Loch Ness Monster of reloading?
Two, what process do you typically use to adjust charges to get from a published bullet weight/type to the bullet weight/type you want to be at (say, data published for a jacketed 115 and you want to get to a coated 124)? Educated guesses? Regression analysis of the data that are available? Some rule of thumb? Starting well below minimum and working up slowly? Randomly loading and firing shit you read on Enos? Paying someone else to fire the test loads you made using the previous option out of their gun?
Bonus less-theoretical specific n00b questions:
- Why did they pull the data for WST in 9mm, given that so many people are successfully using it? Similarly, why isn't there a published 147 gr load for N320?
- Internet seems to suggest that you can pretty much always safely use the lower end of jacketed data for coated/lead bullets; is this a real fact?
- Obviously barrel length affects FPS; can it typically affect it enough to make a load that's safe out of a 4" barrel unsafe out of a 5.5" one?