Rapid Reload, Paper Cartridges and Fast Musket means you should be reloading as a free action, so that shouldn't be an issue. If you're than concerned about moving and shooting for lots of damage, I suppose Vital Strike is an okay substitute, though you'll need to pick up Improved Vital Strike at 11th to keep it relevant. Though, since you're using a musket, between Distance and Steady Aim, you can shoot out to 90' and still be making touch attacks, so I don't think you necessarily need to worry so much about having to move into range so much. On the other hand, Vital Strike is too limited to compare to a full attack in terms of damage, since Vital Strike will only boost the dice rolled, not the bonus damage which is the real meat of mundane attackers, so I would still consider Hammer the Gap + Rapid Shot.