One of the things with muzzleloading, round balls, and ballistics of those, is that the whole system in not very efficient comparatively speaking.
Now before anyone gets their knickers in a knot, just listen.
Black powder is very inefficient as a gun propellant--that's why the inventors kept looking at new smokeless powders that pack more energy per grain and were consumed almost 100% in the fiery ignition of such. Also why inventors came up with pointed bullets and boat tailed bullets, and faster twists to keep these inherently unstable projectiles from flipping around and tumbling like rolling dice.
What was said about a round ball is true. It is a ballistic anomaly, as it really requires ZERO spin to go straight, BUT there are voids, and sprue nibs and tears, and some round balls are not as "round" as others, and every one doesn't weigh the exact same amount as others of same diameter. It is only these variances in the round ball that make a rifled barrel shoot them much better than a smoothbore.
IF we REALLY had high quality smoothbore barrels and absolutely perfectly round balls with ZERO weight tolerance and could load them without distortion, and very consistently, and some of the better match grades of black powder that used to exist--we could shoot them just as far and as accurate over the effective distance of the muzzleloading gun--which is really about 125yds.
Yeah, I know a rifled barrel can shoot a round ball farther and make hits and all that. I have been around for a while. But "apples to apples", a smoothbore is just as accurate as a rifle within those confines and limitations.
The reason for using all that powder in a Zephyr or ANY gun for that matter is that relative to the results, powder is cheap enough that you can use much more to get very few additional fps of velocity. Those few extra feet per second come at the expense of high recoil, more fouling, more smoke, shorter gun life (parts break and wear faster), you get the picture...?
A smoothbore can tolerate more powder than a rifle, and those shallow rifled very slow twist barrels are better for heavier powder charges as they are getting "almost" back to being a smoothbore. Very little added spin is needed to keep a sherical projectile stablized--since it is the most inherently stable projectile to begin with. Now, whether that is why the poor ballistic efficiency is the trade-off is unknown. A round ball loses SO MUCH velocity so very VERY quickly that you should "rarely ever" look at ballistics beyond 125yds, if you are being truly realistic about the whole thing. Look at a ballistics chart that shows the trajectory of a max velocity round ball and a max velocity maxi ball (or other solid base conical) and see how far the drop differs at 125yds. I bet you'll find that there is so little difference that it "should" make you wonder why you bother with the conicals... the difference is retained energy, penetration, or expansion characteristics of the conical. The round ball is the round ball is the round ball. Conicals do very different things depending on how fast they go and what they hit and their composition or nose profile. They are NOT the same in that respect.
NOTE: I'm NOT even going to mention saboted rounds as they are not traditional and intended for extremely fast twist guns of "more modern(?)" designs that none of us should be talking about anyway. IF you want to know why the "I" word is so much of an distorted image of the traditional muzzleloader, it's because of that very fast twist and what projectiles and propellants they use... NOT because there weren't "I" guns made 300yrs ago in very small numbers. Enough on that subject.
If you plot (graph) the energy figures of round ball loads versus the charge weights, you should end up with a linear progression. Doesn't work for the velocity numbers every time, but the energy does seem to work out that way.
FOR AN EXAMPLE: You may only gain an extra 50fps for the next 10gr increment increase in your powder charge, compared to the 100fps increment that you just saw from the last 10gr increase. Starts to make you think that you're wasting powder (and you are up to a point); but if you look at the graph and line plot when it starts to decay or deviate from the next increase--then THAT, is where the efficiency ends.
That cut-off point may be much lower than you want it to be in a particular gun, OR it may be MUCH HIGHER than the mfr's. recommended maximum powder charge. But it is the only objective indicator that I've found that shows me where the most efficient load is at for a particular gun. Remember too that we are talking black powder and round balls ONLY here--which IS what we should be shooting 95% of the time anyway. I'm excluding or excusing conical use in those military guns that were intended to shoot conicals primarily and those guns such as the Whitworth that were very much ahead of their time.
Now all that said, I have not shot a .62 per se, but have shot ALL of the other calibers from .32 up to .72 and most in between. Never owned them all at one time, as I don't have the wherewithal to maintain much selection--I always used what I currently had to trade up/down/across to what I wanted to have next. From the headaches I've heard about from guys with very large milsurp gun collections, I am doing a smart thing, but just having no more than what I actually can use at any one time. I'm not meaning that as an insult to anyone here with a large or small contingent of muzzleloaders either. If you have 6 or 60 or only 1, doesn't matter to me, they are YOUR'S, as such are YOUR BUSINESS ONLY!
I hope I have shed some light on the question that you have and I'll just say that most any muzzleloader smoothbore or rifled, match-wheel-flint-percussion-or other kind of lock gun, in ANY round ball caliber from .32 to .72 is basically going to have the same ballistic path from 0 to 125yds IF they are using approximately the same range of velocities to begin with.
Do NOT use this as a loading recommendation as my figures are for an EXAMPLE: A .45cal round ball of 128gr with a 70gr charge of FFFg at 1800fps, and a .54cal round ball of 224gr with a 100gr charge of FFg at 1650fps... are BOTH going to have the same "basic trajectory" at 125yds. The difference is so piddling as not to matter to a realistic shooter. You can believe this or not, but I have seen it time and time again. And if you have shot long enough, and done as many calcutions and ballistic testing as I have then you will most likely come to the same conclusion.
The only reason to have a bigger caliber--is to have a heavier ball hitting bigger game so you get a quicker stop/kill (especially if the wounded game can fight back!). Likewise the only reason to have a smaller caliber--is to conserve lead and powder and to NOT obliterate smaller game with too large a ball.
I am NOT so silly as to suggest that a .32 is less accurate than a .45 or a .54 is a lot more powerful than a .50 cal. Those are things that are more specific to individual gun performance. But the potential for their comparative accuracy is pretty close.
Sorry about the long read, but I felt this was important.
WV_Hillbilly
I use 160 gr of Goex FFg in mine and it crono's at 1641 fps at the muzzle. :: Hope that helps.
