Just a note of clarification so as not to confuse students:
Batteries are rated in ampere-hours, not amperes per hour.
Come back to the motor lab one afternoon and we can do that. The duration of the spike will naturally depend on the load and the load inertia – probably just a few milliseconds when the shaft is free.
Invitation accepted. I’ll contact you to work out the date/time details 
We had a similar situation last year. We borrowed a Tripp-Lite PR-60 power supply from my company. We connected it directly to the robot in place of the battery when we were trying to dial in the shooter. I just looked up the PR60 and it costs new for about $282 from Tripp-Lite (http://www.tripplite.com/en/products/model.cfm?txtSeriesID=841&txtModelID=244). If you do not need 60 amps, they have smaller power supplies.
Our team did something like this to tune our shooter motors. We used a Tripp-Lite PR-60 power supply I borrowed from work. We connected it directly to the robot in place of the regular battery. We were only running the shooter motors (had the robot up on blocks to prevent any moving) and it worked great.
A new from the manufacturer PR-60 is about $280.
PR-60 Power Supply
If you do not need a 60 amp supply they have a 10 amp for about $80.
PR-10 Power Supply
The 40 amp snap action breakers are a thermal device. When the current is high the device heats up, when it gets to s specific temperature it breaks contact. Since it’s an automatic resetting breaker, when the temperature cools down it will reengage the contact. The 40 Amp specification is a requirement that it will NOT break contact below that current. Above 40 Amps it WILL break contact, but only after a specified time (at 132 Amps it’s just under 1 second).
Do not use the above power supplies to charge batteries. They do not have a current control and do not have an automatic shutoff.