...do you think the paper would be thick enough to impart spin?
Would the paper not be strong enough so that there would be blow by and lack of accuracy? ...
Nope....
Have not tried this at the range yet but I thought I would ask if anyone has attempted this.
Hessian Jaegers would do it all the time during the AWI.
What they would do is either have a separate pouch with the balls already wrapped in the cloth or leather patches, with a bit of thread to hold the greased patch cinched around the ball over the sprue. They would draw a powder only cartridge, pour it down, then they could ram the paper as a wad, followed by the pre-wrapped ball, OR simply discard the empty paper tube and load the pre-wrapped ball. The thread breaks when the ball is launched, and the patch falls away.
The other method was to place the pre-wrapped ball into the cartridge at the bottom, sprue/sewn end down toward the end of the cartridge, then load the powder on top. To load the rifle they would remove the ball by biting the ball portion free of the cartridge, pour the powder down, and then spit the ball into their hand for loading on top of the powder with the ramrod. The paper bitten off with the ball would come free during the loading.
The paper alone doesn't work because there is just too little surface area on the ball for the paper to contact both the ball and the interior wall of the barrel. A patch by virtue of its being wrapped around the ball, even though it doesn't touch any more of the interior of the barrel wall than does the paper, it is strong enough to grip the half of the ball where it is kept tight during loading.
making paper cartridges of powder and using a loading block holding a few ball wrapped in greased patches works well along the same lines.
LD