Here's the straight goods...muzzle loading guns use BLACK POWDER. NOT REPLICA BP EITHER!! You don't put gasoline in a diesel engine.
past that and to the question .
Let me also say that im kind of leery of discussing this here as I don’t think the topic actually fits what this forum or organization is all about .
Barrel steels have changed a lot through the years . One of the reasons for that is that barrels had to stay up with the performance of the powders . When it comes to smokeless , you have to know what your buying . What Cal your buying it for . You don’t just go buy a powder off the shelf , weigh it out and load it into a shell .
If you do you can blow up a modern barrel just as easy as you can by loading smokeless into a muzzleloader.
Also as was mentioned BP is measured by volume not weight.
I disagree with the thought that BP cannot reach pressures of some smokeless . It in fact can given the right environment. But we also have to keep this in some context . So if we are saying that BP wont produce the same pressures applied to the same amount in the same bore/ cal while backing the same projectile , then yes this is true .
Whats also true and im sure is in the mind of the person posting this question .
Some smokeless powders can be reduced to provide pressures in the normal BP performance range . But the problem , just as is being now seem in the smokeless designed
Market, people being what people are , they want to constantly push the envelope and thus don’t continue to follow what they have been told . Thus in a very short time they exceed the design applications . If one doubts this , all they have to do is take a look at the number of folks already using different smokeless powders in the modern designed smokeless muzzle loading guns, instead of sticking to what the manufacture has stated they need to use . Thus its IMO only a mater of time before things start to happen . Those designing these guns will end up being the ones catching the flack .
The other issue is not one of the type of breech , but the breech design itself .
The internal breeching like we use for BP is being used with success . but again what is different is the design of the breech . The breech is also easily removable and regularly replaced . It has to be because of the increased effects of gas cutting found with the application of smokeless powders
Then we step back to the action . A side lock just isn’t strong enough to withstand the pressures that it would or potentially could encounter. This is why the applications designed for smokeless , use a bolt with at least 1 locking lug even though the rifle is using an eternal breech with either a nipple or a casing type ignition . In fact if you research these designs to there base , you find a double locking lug as part of the original design . The removal of that 2nd lug for the marketed design most times is part of fulfilling a regulation
As to the projectile being engraved . This application has little to do with the powder and more to do with the application of the cartridge and the desired accuracy of that application .
Again if we take some time and look at whats marketed today we will see that the smokeless guns in the muzzle loading market are not using paper patches or false muzzles to load the projectile and they are getting high accuracy .
Now with the above being said , I would not recommend trying to apply a smokeless powder in the application of the guns found on this forum . If you do you asking for big issues and trip to the hospital or funeral chapel. Be use using a modern barrel capable of pressures of smokeless or not is not the only consideration one needs to take into account .