Also, the Savage plug is very different from any other plug on the market. The same feature and effect that makes it safe keeps it from transferring as much energy from the primer to the powder.
Most breech plugs have very little internal hollow space/volume from the front edge of the primer to front edge of the plug (where the powder rests). In contrast, the Savage has a internal open column approximately 1/4" in diameter and approximately 1.8" long, and it's capped with the vent liner with only a .030" diameter hole. Without the ventliner, when pressure in tehe barrel jumps up to 30,000 psi, give or take, and then begins sloping off, pressure at the face of the primer would always pretty much equal to the barrel/"chamber-area" pressure.
In effect, this design of the Savage plug acts as a pressure delay chamber, in much the same way as a car muffler does. Gases under 30,000 psi of pressure, give or take, are going to flow through a .030" hole at a certain rate of speed. But, it is flowing into a chamber (the space running from vent liner to primer) that is 10 times larger in diameter--and remember, because it is a cylinder, volume increases exponentially with diameter. It takes some amount of time for a sufficient volume of gases to flow through the .030" hole to fully pressurize that chamber. Granted, the amounts of timer we are talking about are measured in milliseconds, but the time differentials are still there.
So, the entire time the pressure is builing in the barrel, the pressure in the plug chamber/space is lagging behind it. Then, when pressure in the barrel peaks and starts falling, pressure inside the plug chamber/space does not climb to the same peak as the barrel saw, but immediately reverses and starts following barrel pressure back down.
This means that pressure against the inside face of the primer never reaches the same peak as pressure inside the barrel. This is a good thing, since 209A primers were designed to handle the much, much lower pressures of shotguns, and it keeps more pressure off of the bolt face.
The flip side is the flame/gases from the primer detonation encounter the same obstacle to lighting and pressurizing the powder in the barrel of the 10ML. Obviously, the 209 primer does this and does it well. Nevertheless, while a large rifle or small rifle primer may work well with blackpowder in other rifles, or might work well with smokeless in a different muzzleloader with a different style plug, I don't think that the "muffler" effect of the Savage plug would be conducive to use of weaker/smaller primers.
