Subject: How do I calculate the velocity of a projectile exiting an solenoid?

I know from experiment if you apply current to an electromagnetic solenoid, 
place a small projectile (ie BB) in one end, and remove the current when the 
projectile passes the middle, it will continue out the other end.  My question 
is:
Given a solenoid of a specific size (length, number of turns, etc.), a specified 
current, and projectile of known mass and material,  how do you calculate the 
acceleration / velocity imparted?

Re: How do I calculate the velocity of a projectile exiting an solenoid?