As far as I know, you'd be correct on everything you said above. My sense is that pellets,for their weight, help to reduce pressures. They seem todo this byexposing a more limited area to burning in the early stages of burning. As they burn, they will tend to granulate exposing an increasing surface area to flame. Pelletizing powder seems tohelp to burn a given weight of propellant progressively, meaning that, the rate of burn is slower in the beginning and increases for a period of time after ignition. For a given weight, loose powder will peak sooner in time (at a smallerbreech volume)leading to higher peak pressure. So a charge of pellets will have a broader pressure curve with a lower peak pressure while the same weight in granulated powder will have a spikier pressure curve and higher peak pressure. Of course I think this describes the design for loads which are approved by Hodgdon. If you load beyond their recommendations,then I don't have an opinionabout whats going on.

On the subject of .45 cal. The .50 cal bore has approximately 24% more bore area than the .45 cal. bore. This means for bullets of the same sectional density, one can, in theory, increase the charge in the 50 cal by 24% (with respect to the .45 charge) and yield the same peak pressure and the same muzzle velocity. Say you shoot 240 grain bullet in the .45 cal with 80 grains, peak pressures and muzzle velocitieswill be similiar to a .50 cal loaded with a 300 grain bullet and 100 grains.

On the other hand,load 150 grains of Pyro pellets and a 275 PB in a .45 cal.THEN thats like (in terms of expected peakpressure) loading 180 grains of Pyro pellets and a 348 PB in a 50 cal. These loads not approved by Hodgdon nor recommended by me.

Loading 100 grains RS and a 325 conical in the 45 cal, is like loading 120 grains RS under a410 grain GP in a 50 cal. These loads also not approved by Hodgdon nor recommended by me.

For the waysome folks load, pressures are running higher in .45 cal rifles than they may expect they are.