Here is an update to the Nerf Stampede Voltage Increase and RoF Testing.
I have test fired more clips and have found that voltages of above 20 Volts produce way too high a rate-of-fire to be able to reliably chamber foam darts from clips and magazines. Although some clips might be able to fire properly once in a while, the majority of clips will get jammed easily very often. Just a slight delay in dart advancement or a bent dart can cause jams to occur.
Testing with 18 Volts provided more manageable speeds, the rate of jams occurring is less but it still happens, especially when worn-out foam darts happen to get stuck in the clips. Not a good situation to be in during a Nerf game!
Overall, i've found 15-16 Volts to be just right in terms of improved rate-of-fire, yet with smooth operation and low chances of jams occurring, even when slightly bent or damaged darts are used. Therefore, i'd recommend using 15-16 Volts for reliable operation in modded Stampedes.
With that note... here is a Clip Reload & Test Fire video of a modded Nerf Stampede running on 15 Volts.