Sharpsman, let me give you some "facts" about the Savage, muzzleloader. I think I am more than qualified to give you the "facts" as I am the one who invented, patented, and worked with Savage to market it.
First of all, the breech plug is as long and short as it needs to be. Like edge said, and he has much more experince with the Savage 10ML-II than you ever will, the breech plug is long enough to get the powder charge area past the threads of the barrel nut, for maximum strength. The original 10ML, used a percussion module, that fit into a chamber in the breech plug. The 10ML-II kept the original specs of the 10ML breech plug, but did away with the module. The vent liner was designed to limit the amount of pressure and prevent excess pressure from blowing back into the module and/or primer.
As far as inconsistant ignition, goes in 17 years of shooting this exact same style breech plug, I can count the ignition failures on 1 hand, and still have enough to spare to pick my nose. The 1.5" breech plug works as designed and if one is at least 10% smarter than a lug nut, one will have 100% reliable ignition. Use the correct primers, the correct powders, and the correct sabot/bullet combination, you can hunt from the Artic to the Equator, with zero igniton failure. Drop the firing pin on an unloaded Savage 10ML-II, with just a Federal or a Winchester 209 primer inserted and you will see the flame out the end of the 24" barrel. You cannot tell me that the breech plug is to long and the flame is not getting to the powder charge. The 55,000+ rounds of smokeless powder muzzleloading, tells me you are blowing smoke on this subject.
The assinine qoute that BP is thge most accurate powder ever invented, may have been true prior to 1891. Like Edge said, if that were true every benchrest shooter in the world would be shooting it. As far as battleships use it, they as well as field artillery, use a BP booster charge on the base (the Red Pad) of the main powder increment. It is just to aid in the ignition of the main smokeless powder charge.
To WSmitty01, I hate to break it to you, but you are dead wrong. In fact the total opposite is true, in that every year more and more states are allowing the use of smokeless powder in muzzleloaders.
That all I have for now. Let me know if I can clarify anything else. Out here.