It does seem counter-intuitive that a lighter lower velocity load would have better penetration than a load using a heavy charge of black powder. At some point though, with pure lead round balls, the higher velocity expands the ball so much in flesh that sectional density is totally out the window, and penetration is lessened. I noticed that a higher velocity very expanded lead round ball did a lot of damage and dropped deer quickly. But often the flattened ball would be found under the hide on the off side rather than leaving an exit hole. With less than perfect shot placement, having only an entrance hole makes much less of a blood trail, even though there may be massive hemorrhaging internally.
Everything about muzzleloading involves compromise. A lead round ball isn't moving very fast under the best of circumstances. If you try pushing the limits on range, they start dropping rapidly after 125 yards or so, and reducing velocity permits them to drop more at longer ranges. Once you sight in at say 100 yards, try moving the target back to 125, 150, and 175 yards to see the impressive amount of drop. But that's not really a problem in most Pennsylvania woods hunting.
And if you are missing deer with that .54 flintlock, one thing to remember is that a roundball from a muzzloader is not as well stabilized as a bullet from a high velocity rifle. It doesn't take much to deflect a roundball. I've missed a few shots at standing deer when I had a perfect hold and trigger squeeze. In every case, if I looked hard enough, I'd find that I nicked a small branch or sapling between me and the deer. The amount of deflection is much greater if the branch you hit is closer to you than the deer. So pick an opening carefully when shooting in the brush... which is about 90% of the time. This is just part of what makes hunting with a flintlock more of a challenge. For some beginners, half the battle is just getting it to go off, even when it isn't raining. And if you are getting any delay to speak of between pulling the trigger and having the gun go off, then you are doing something wrong. That flintlock ignition delay is an old wives tale. The difference between a flintlock and a percussion is mere milliseconds if you are loading correctly and have a good lock, frizzen, and flint. Any appreciable ignition delay gives too much time for your sights to wander off target.
