I've not heard of the formula, Kermit, but it certainly gives a healthy charge prediction. The loads, 120gr. in a .50 and 140gr. in a .54 I find quite intersting as they are very close to the charges I recall from back in the 70's and 80's. There is a reason for that, but it wasn't due to a formula such as you've provided. It was due to working up to a load that provided the best accuracy at 100 yards on paper. The shooting wasn't on gongs or tin cans or old TV's - a gong or TV has too big a 10 and X ring to tell anything meaningful. Ricochetts knock cans all over -without meaning. Paper is needed to see what's happening with every change.
I do find it intersting this formula came up with what we found through actual testing. Yes - they are heavy loads. Yes, they were accurate. No-they don't shoot to the same point of impact as your 25 yard load.
I've never lost accuracy (w/qualifier) by adding more powder (within reason for the bore size) - IF (not 1F) and it's a big IF, the ball and patch combination remains viable, meaning the combination can handle the increased pressure.
(qualifier)- I found I needed heavier/thicker patches and balls only .005" under bore size when desiring the best accuracy- which meant heavy loads.
Most people find fouling increases with heavier loads (their patches are failing), therefore accuracy is lost past a certain level of powder/velocity. With the tighter combinations we usually use & increased powder charges, I find patch failure doesn't happen, but what does happen, is accuracy continues to improve until we cease adding more - ie; that's enough- and it comes very close to the predictions you've given, Kermit.
If I think back to the days when we mostly shot 100 yards or further, I recall we all loaded heavier than today. We were surprised people actually shot at targets a mere 25 yards distant. We were used to using heavy charges as we found they were needed to maintain accuracy at the longer ranges we normally shot - no big puzzle there.
Today, it seems people put great stock in 25 yard shooting & even do load develpment at that range while the more experienced know this is but a waste of time and powder. Those who shoot mostly close ranges can usually be identified by small for calibre powder charges as they've 'usually' never really worked up an accurate load for their rifles. Some are happy with whatever accuracy they get with an arbitrarily picked load combination and that's just fine.
Those who desire the best their rifle can give them, need to know the can get it, but will have to work up the best load themselves and that usually means tighter combinations and much heavier loads - especially for the longer ranges.
