There is nothing wrong with working up a load with a round ball made of lead alloys. The key phrase is " Working up a load ". The problem with alloys is keeping them the same, so that the size of the balls do not vary from one batch to another. Alloys shrink and expand at different rates, so " working up a load " is much more difficult to do, unless all you are doing is shooting soft ball size groups at 25 yds. Then it doesn't matter.
With a rifle, I always thought the point was to have a long gun that shot tighter groups than I can shoot with a smoothbore. If you are just shooting at short ranges, at large targets, you can do that with a smoothbore, and probably hit your targets shooting rocks and nails ! Buy a blunderbuss with the belled muzzle to make it easier to load the rocks and nails. Its will be a lot of fun to shoot, and you surely will hit anything you are aiming at out to 25 yds.
Hard cast balls do have a place- particularly when being used in a LARGE BORE gun to kill dangerous game, where penetration is paramount in importance, and expansion is less so, simply because the diameter of the ball is so large to start with. If you are hunting bear with a 10 ga. 8 ga. or 6 ga. gun, rifled or smooth, it would make sense to cast an alloy ball with tin in it. If you can leave the antimony out, the tin will make the ball harder, but it can still expand in tough flesh and bones. With antimony, it may be so brittle that pieces of the ball not only flatten, but crack off, reducing the weight of the projectile as it disintegrates, and reducing the amount of penetration accordingly.
We use pure lead for casting balls for the typical rifle because they are pretty regular in how they come out of the molds, both in diameter and weight, expand quickly even with low powered loads, to fill the grooves in the rifle, and expand well in game animals for a quick kill, even when fired with lighter loads. The only reason that we work up a higher velocity load to use with a PRB is to flatten the trajectory, so we are more likely to hit our target or game in the kill zone, regarless of the range out to 100 yds.
With modern guns, we increase velocity to flatten trajectory on already flat shooting guns, so that we can EXTEND the killing range of the gun to several hundred yards. We may never need that ability, or ever take a shot at long rang, but we want that option( or so we tell ourselves.) Because the small diameter bullets we shoot in modern guns must be traveling fast to have a double shock wave coming off the bullet when it hits game to cause massive hemorrhaging in the animal for a clean, quick kill, we stoke up those powder charges, and try to get every bit of velocity a particularly designed gun and action type will hold. We probably don't need all that speed and energy, and thw law of physics is not suspended for modern cartridge guns- things that leave the barrel faster slow faster- but we like to dream of owning a rifle that is capable of shooting game farther than we can see without having to adjust our sights. Its silly, but that is why we call this a sport. It allows us to be silly until we discover that we CAN'T change certain laws of physics no matter what we do.
Most people who began shooting modern guns before coming to Black Powder finally learn that what really attracts them to this sport is not the extra hunting season, but the quiet slow deliberation which is necessary to load these guns to get the most accuracy out of them. There are lots of little things to learn that are each important in themselves before you get the best accuracy with Black powder guns. Its a challenge to learn them, and when you put it all together, you find out that you are a much better hunter, and shooter- even going back and shooting cartridge guns- after you have mastered a black powder rifle.
