bwinters and toad;
Because it's very late and a long day ahead, I'll not respond in detail just now.
You both make some valid points... up to a point. I'm in no way talking about small cases "beating" larger cases. Or even promoting it. That's not what this is about.
It's not about "magic" either... that's insulting.
I've been a hunter for about 60 years, but I started handloading something over 30 years ago. In that time I've loaded many well-known cartridges from the 22 Hornet to the 458 WM. I think a total of 2 primers were blown, and that was due to a book load for a 35 Whelen.
Two other book loads: one in 375 H&H gave me 2700+ fps from a 300gr in a 26" barrel. Another gave me 2842 fps from a 250gr in a 338 Win Mag with a 26" tube. No apparent problems with either. No cup or psi numbers were given by the books.
Re: the 500gr Hor from 53.1 grs IMR 3031 in a Ruger No.1 45-70:
Hornady says: 1800 fps @ 50,000 cup.
Lyman says: 1879 fps (26") at 39,000 cup.
I'm not questioning your book knowledge, but frankly the books don't often agree, and sometimes that disagreement is pronounced. I make it a point of talking directly to chief ballistic engineers whenever possible, and what I've found from my personal experience and those conversations is that there are too many variables and anomalies to predict what is happening, or going to happen, in any given series of tests. One reason being that they don't have the time or resources to test everything, so projections are given.
I mentioned that the head ballistics guy was surprised by the results from a load they tested for me. But, in fact they had to seat the 500gr Hor 1/10" deeper than my specs because of a shorter throat. Everything else was the same except for 2 factors: their COL was 2.83" and mine was 2.93". They used a 24" test barrel and I was using a 22" Ruger barrel. They got 2100 fps and I was getting just a tad over 2000. Their psi was 63,200 avg and he said mine would be less, and safe! Extreme spread was less than 10 fps. I checked with a Ruger rep, asking about the strength of that rifle (No.1 in 45-70)and he said, quote: "It can be compared to our .458 Win Mag".
Some of the things you didn't address: barrel length and COL. I've read Hodgdon's numbers, and as many others as I could locate, including Nosler. That doesn't mean too much as they HAVE to respect the strength of old rifles and brass made for CIP specs. You know, I believe, that 50,000 cup for a 30-06 doesn't represent it's full potential with modern components and metallurgy. You also know that 57,000 cup doesn't represent the full potential of the 9.3 X 62 in modern rifles with the best modern components. When you quote 2600 fps for the 375 H&H... that's not news! But that's from a 24" barrel.
In your estimation, what would you get from a 22.4". I got 2530 to 2550 (pushing it) with the best powder of the day from a 22". You are addressing me as though I'm some kind of irresponsible person! There are others on here, and elsewhere, who freely admit they are getting OVER 2500 fps from 286s. Check, please, RealGuns, where they received OVER 2500 fps for 285s and 286s using RL-17.
I've nowhere implied my tests were final, au contraire mon ami, I've stated on my blog that MORE testing has to be done.
Nonetheless, I'll stand by the notion that there is little difference between a 300gr/.375"/.305sd at 2550 and a 286gr/.366/.305sd at 2500+ fps! If RealGuns is free to publish their findings without giving cup/psi, then so will I!
In 32 years of handloading, 2 primers blown and no guns wrecked or people hurt (except for the animals)
I think I'll just carry on...
Bob
www.bigbores.ca 
