Dear CVA as a fan of your muzzleloaders I regret to write what I'm about to write, however if someone gets hurt because of others not speaking up I sure would not feel right about that. I've been a big fan of the Acura 50 cal 1 and 28 twist five different rifles I shot each for a year and then I gave them away to help others learn .I was excited about the Paramount 45 Cal I brought one of the first ones to come out shot it a lot,, ended up just putting it in the closet because of the bore dimension's
CVA chose from the beginning to make their 45 bore fit their bullet,, I suppose in a business conceptual sense that seem smart,, I do not think they thought through that concept thoroughly . What will happen when an inexperienced shooter chooses to try a different bullet than the factory recommended bullet,, can an inexperienced shooter rely on the bullet to stay seated firmly on the powder column? And what about some of the paramounts that have such loose bores that even their factory recommended bullet is risky about staying seated? I just purchased a MRX Acura 45 Cal 1 and 22 twist the only bullets I can safely seat in this rifle is the factory 280 eld all other bore riding bullets and even 40 cal bullets in a Sabot are too loose in this rifle. I know I guess many will say send the rifle back the problem is I'm convinced that this problem is not just in the rifle that I brought every Paramount shooter that I've talked to the last couple of years has the same issue an oversized bore I'm convinced all of the Acura 45 Cal rifles that are currently being sold here in America have the same bore dimensions or similar, again if you're only going to shoot their bullet I guess everything might be fine but it seems like there's some issues even with their bullets. The Paramount has enough barrel shank and a strong enough barrel that maybe somebody could get away with the bullet falling off the powder column and still firing the gun, the Acura with the thinner barrel worries me I'm afraid someone is going to lose a hand or an arm.
Again to those at CVA if you change your bore dimensions back to an American 45 cal guess what your bullets will still work in the rifle you can still sell your bullets!!!
I will say this to all of you considering buying one of their 45 Cal 22 twist I would really think hard you're going to be very limited to what you can shoot in that rifle ,,will they shoot the 280-285 elds accurately I believe most of the rifles that you buy will ,,are you going to be able to shoot another bullet in it safely I do not think so and I sure am worried that someone inexperienced buying that rifle is going to be missing a hand. Just my personal opinion but I would not buy that rifle unless you are a very experienced muzzleloader shooter, to those that are I don't think you'll have any problems,it's the inexperience person trying a rifle out new that I'm concerned about.
I'm pleased to find this forum and as a newbie here I'll simply say that in the past I did a whale of a lot of posting at several ML forums.
So allow me to politely jump in with both feet here. Contrary to common knowledge, having space between powder and bullet is not an "obstruction" situation, and instead creates, via internal-ballistics principles, a larger powder-volume space. That means lower, not higher pressure is created by the ignition of the powder. There is, very rarely, an issue of "detonation", a poorly understood phenomenon in smokeless powder rifle loads wherein the primer flash might travel over the surface of a "leveled-out" powder load and thus ignite it far too fast, creating a highly excessive pressure peak. But note that is smokeless powder, and very rare.
So, using BP in caplock or flintlock MLs, or in an inline rifle, or Pyrodex, Triple7 or Blackhorn 209, will mean poor pressure buildup if the bullet migrates forward of the powder charge. And with the marvelous pressure capabilties of BH 209, its tendency is to ignite poorly if there is diminished restriction to its burning, such as a loose bullet, oversized bore, too-small sabot, etc. That means lower, not higher, pressure. Additionally, for what it's worth, BH 209 has a virtual duplicate of BP's pressure curve, meaning it is a very quick peak followed by rapid pressure drop-off. It also means that BH 209 is more likely to produce bullet oburation and hence fill the rifling grooves, than the other BP substitutes do, and gives it the remarkably low ES (extreme spread of velocity) in any given string of shots (provided that the bullet is tight in the bore via its initial diameter, sabot, skirt diameter, or bullet obturation at ignition).
In the later 1840s, there were some european MLs with typical soft iron barrels that had an iron post projecting forward from the breechplug (Delvigny style), intentionally creating a space between powder charge and bullet!
As far as undersized bullets, the ML ones that look jacketed are instead soft lead that has a thin copper coating to lessen fouling and look nice (read, cost an excessive amount). They are designed to obturate upon ignition of the powder (yes, that happens before the bullet even starts to move, which was proven by Dr. Franklin Mann in his 1902 book).
In closing, blown up barrels are virtually always caused by an actual obstruction in the barrel, which a fired bullet or shot charge meets, thus producing an instant pressure spike that may blow up the barrel.
Aloha, Ka'imiloa