Fast Transients/Burst Immunity for SCR

Although the problems of preventing SCRs from turning on when it encounters high dV/dt transients are extensively covered in various publications and websites, utilizing RC snubber circuits, these documents normally discuss the applications for motor control, flyback, switch mode power supplies, etc. These applications are mostly for AC systems and very seldom investigate the fast transients/burst protection schemes for equipment that needs to comply with IEC 61000-4-4 in an DC switching environment.
In an application where a SCR is used to discharge a capacitor into a low ohm pyrotechnic device, in a very electrically noisy environment, proofs to be a bit of a challenge. The equipment must comply to the IEC 61000-4-4 (Level 4) specification for Fast Transient/Burst immunity. In this test, the lines driving the pyrotechnic device are subjected to a transient waveform of 50ns at 2kV with a repetition frequency of 5 or 100Khz. Using a BT152B-600R SCR, 4700uF capacitor charge at 24V and using a 0.1uF 400V polyester capacitor, 22R 2W resistor as snubber across the SCR, the objective was achieved in preventing the SCR from switching on during the application of the fast transients, even at 4kV.
The question is: Is this the optimum snubber design? The capacitor and resistor values were randomly picked and no calculations were performed to determine the optimal values.