So bear with me this is kind of a weird/different question. A 308 win can't push a 168gr bullet as fast as a 30-06 just as a 30-06 can't push a 168gr bullet as fast as a 300 win mag because of case capacity with current powders. So my question is why couldn't there be a powder that say could produce 30-06 pressures in a 308 case size or even 300 win mag pressures in a 308 case size. I guess what I am really wondering is the barrels are really the same just the chamber being reamed for what ever cartridge correct? Is it because of the time it takes to make the pressure? I know this is a very different kind of question. Just the kind of shit I think about when I am at church.....lol
First, you have to understand the basic principle of smokeless powder. The burn speed was determined by the size of the kernel, or ball. The nitrocellulose used burns at the same speed, but how much of it burns at a time was dampened by thickness and length of the kernels or ball. Nitrocellulose alone is called single based powder. Then we get to double based powders, where nitroglycerin was added. This adds pressure. All ball powder is double based, i.e. Win 748 and 760, but there are "extruded" double based powders, i.e. Alliant Re-10/12/15/17/19 etc. Double based powders burn a little slower but since they produce more pressure, they SORT OF equivalate to extruded single based powders. But, because of pressure differences, they DO NOT convert straight across. Interpolation can be used as a means to find a starting load if you cannot find data to work up from. But, you have to understand the comparisons of different cartridges and the powders you are comparing in them to find the minimum load to work up from for your bullet/powder/cartridge combination.
That said, You've already seen the first generations of "super powders". If you were to take the old IMR and Hodgdon powders (made by DuPont, who owned IMR) they were like metering boulders through the powder measures. The size of the kernel was how they determined burn speed. Then, along came the Hodgdon Extreme line-up and you would see a HUGE difference. The kernels are roughly half the size. The kernels are spray coated with a burn retardant to slow the burn. They are pretty much all new powders. But, to avoid too much confusion, (continueum marketing) they maintained the old ID numbers as that is what they were chemically formulated to duplicate.
The "even newer" generation of powders does basically the same thing, but they mix the burn retardant integrally (RE-17 & IMR 8208 XBR). Spraying on the burn retardant gave a good replication of the intended powder, but burned off quickly. Mixing the powder throughout the kernel/ball has made the chemical breakdown, or rapid oxidation of the burn retardant much smoother. Both of these tend to give what I call a "soft pressure ceiling". Burn retardant is basically inert chemical that won't react until it hits a certain pressure or temperature. Then that molecule "cracks" and free radicals go off to join other free radicals and make a new molecule. One example of this is molecules heavy with hydrogen, which combines well with carbon, and oxygen (think rust, feris oxide). Once temp/pressure get high enough then the hydrocarbons and oxy-whatever molecules break up. Hydrogen and Oxygen LOVE each other and make water...cooling the burn. Just a rudimentary example of how this is being done, not that this is the actual formula being used.
With the burn retardants being used today it is important to stop when the book says so, instead of doing what many of us have always done and that is work up until you see pressure signs. A good example is RE-17. You won't see pressure signs until you are way above what should be for the max load. The retardant, as it is being chemically used, will keep pressure down. But, when you've burned through the retardant, you are basically left with a hot load of fast powder. And nothing more to cool the burn. You will go from no sign, no sign, to damn! blown primers!...or worse.
As to super powders, I'm surprised we don't see more liquid chemical propellants that start like how we make det. chord for explosives. It could be poured into cases and allowed to cure hard for ignition.
One big drawback to a number of advancements is the inability to dissipate heat from the firing process. So far brass has still shown to be the best for taking the heat out of the weapon in sustained firing tests. Another big drawback is literally how easy it is to make smokeless powder vs. a lot of other chemical products.