RE: How long can a load be in a gun?
lazyness does not a target shooter make...
The folks "cleanin em once a year whether they need it or not" are only fooling themselves and ruining any chance of their guns staying extremely accurate for decades. Blackpowder and ALL of her substitutes (save for smokeless) are acidic and also attract/draw moisture (whats the word for that... hygroscopic or sumpin like dat?). Your typical 30/06 case laying around is worry free because of several factors but the biggest is that the mixture is weatherproof. The same CANNOT be said for a loaded muzzleloader.
The only way you could be completely "moistureless" would be to load the gun in an extremely dry location. Then immediately place a waterproof plug over the muzzle and nipple areas. But why do even that? How much is the compenents of a load vs the damage using your gun as a big speed loader? Just unload it/ shoot it, reclean it and the load it up prior too her next use.
As was said, are we talking about keeping an already fired gun loaded or a clean one? The benefits of an inline is the removal of the breechplug and being able to unload the gun without firing and cleaning. THAT is the simpleist solution. But its not simple if you are shooting loose powder and cant remove the breechplug with the gun pointed muzzle down. That loose powder is a MESS to clean from the breechplug area because of all the lube in that area. If its already dirty then why worry about saving a load? You will more than likely just end up with a destroyed barrel and a frozen breechplug if you take the lazy road.
And for those REALLY opposed to cleanin em (twould be me in this group), theres the SAVAGE smokeless hehehe! Lastnight after hunting I fired the gun into the ground, threw her into the backseat and went home. Shes only had 10 shots fired through her. It still got 90 more before the breechplug needs to be removed and relubed!!!
RA