m203 shells & CO2

[the hobo clown]

I recently decided to make the jump to co2 with my 40mm grenades and need some help with just how the hell I make it work.
I'm using a madbull xm204 'king' grenade and the s-thunder adapter with regulator nozzle and I am having the following problems:

1: I can't figure out how to adjust the PSI as the allen key seems to make no differene no matter which way i turn it.
2: filling the grenade is massivley problematic; each time i fill it the trigger is incredibly weak and goes off with a pop less powerful than one of my grenades filled with abbey ultra. I've tried filling it for longer but it seems to make no difference. Do i need to use more than 1 12g cartridge to fill this grenade or somthing as this certainly isn't working the way all th youtube videos would have me believe.

any help would be appreciated

thanks