I understand.
Quick question regarding the current you require (47A). If i am reading this correctly the amperage you are referring to is the "stall" current. If so I would suggest you consider something in the 12 - 15A range and add current limiting or likely better for your application, overcurrent shutoff. My current range suggestion is based on the Wolverine motor with a running current of 10 amps.
That being said, I wonder what the actual load will be. Just thinking about it the motors will accelerate from stop, draw a pulse of current when the dart contacts the wheels then be idling for the remainder of the on time.
Depending on the repeat shot time you might want to think about keeping the "launching" motors on for a longer period of time so perhaps they don't have to stop between shots, if the shots are say within 10 seconds.
Stall current is not a place to be running a motor, and probably not a battery. Although I'm sure Mosfets that will handle this type of current would not be an issue.