The following is as I remember it so those who read about it feel free to correct me if I'm wrong.
Several years ago a pair of guy's who wrote a monthly column for "Muzzle Blasts", the monthly magazine the members of the National Muzzleloading Rifle Association receives, tested balls cast from pure lead against wheel weights.
The reason for their testing is their monthly column was usually to answer questions sent in to them and someone asked the same question that this topic is about.
Anyway, they are avid target shooters so they know a thing or two about accuracy and they really expected to see a big difference between the pure lead and the lead alloy balls.
At first, they found that loading the hard alloy balls was very hard to do. Obviously the balls were not deforming like soft lead would do.
Their shooting seemed to say the hard lead didn't shoot as well either until they changed their ball/patch combination.
They found that by decreasing the patch thickness so the ball didn't have to deform as much improved the accuracy a lot.
In fact, it was close enough to their regular soft ball load that it wasn't worth worrying about unless a side of beef or a similar prize was up for grabs.
Now, I must point out that the Bevel Brothers use barrels with slow twists and deep rifling made for shooting roundballs.
They did not test the faster twist shallower grooved barrels that are found on TC's, Traditions and CVA's so their findings might not apply to those guns.
I will say that although the harder alloy balls seemed to work for target shooting, some thought needs to be given to using it for hunting.
Our pure lead roundballs start out big and expand even bigger when they hit an animal and I'm sure the hard alloy like wheel weights would not do nearly as well at this.
That, to me, makes the hard alloys rather questionable for a choice when hunting big game. :hmm: