Very clever, the idea here is to limit the current inrush cause by the bulk capacitor (the big cans) by placing a resistance directly in series with the rest of the circuit.
Chaka’s is placing 333 ohms in series with the rest of the circuit. If he is running a 40V system, that will allow a maximum of 120mA to charge the bulk capacitors and to reduce/eliminate the inrush current once the bullet gets to the end of the barrel.
How do you determine what resistance to put? Well, is 120mA enough to create a spark, I don’t think so. Is 120mA enough to charge the bulk caps in a few mili seconds, probably 90% charge yes. You want that windowed sweet spot.