Pure pewter is tin, but not all pewter is all tin.  Some pewter is an alloy of perhaps 80% tin mixed with copper and/or antimony and/or other metals.

Tin is added to lead mostly to encourage forming better cast projectiles and to add some degree of hardness, and tin will reduce projectile weight.  None of this is needed for patched balls or paper cartridge balls, but can be a good thing for long range muzzleloaders and other such firearms.

No problem, Kevin, pouring pewter is as easy as falling off a log.
Wait!!!  Falling off a log is easier, you don't have to heat anything up.   
But don't expect a factual answer from me, I've never done that either.
Closest I have ever come to that was casting round ball.

Hoping TMA resigns supreme for ever.
 Like I've stated before it's the only BP forum I use so when it's gone I'm gone
 Kevin

For the sake of those individuals, I hope the TMA continues to exist for a long time. Thank you to the remaining founders, and also to those who are no longer with us.

Will do!