I've been shooting black powder muzzle loaders for almost fifty years. I do use a short starter and it doesn't hurt anything. What the short starter does is force the ball into the rifling and engages the rifling into the ball/bullet. Once it's started, and the rifling is engaged, the ball/bullet will pretty easily move down the barrel at that point. Beating on the ball/bullet can, and will, cause the ball/bullet to be deformed to some extent and may effect accuracy. You should never need a mallet to start the bullet. If you're using a mallet your patch is too thick, the ball is oversized, or both.