I think that if you left the bolt and hammer connected you might have velocity problems. When you pull the trigger it's a lot more mass to move forward. This could also be a form of cheating. If you push the pump forward hard you will likely get an increase in velocity. It would be like thumbing the cocking rod on a Sniper, hence why beaver tails are mandatory at most fields for Autocockers and Snipers.
Shooting from a closed bolt will not increase your accuracy or range. Theses are old paintball myths. Pumps are known for accuracy because the people who shoot them tend to practice, aim, and buy the best paint they can.