@gat The amount of gas needed will depend on how heavy the new bolt carrier group is and what ammo you're shooting.
Obviously a .22LR round will put out more gas and have a better chance of cycling than a .22 short subsonic round.
The good news is most stock guns are overgassed from the factory to give them a better chance of cycling well on bad quality ammo so you probably have a decent chance of not having any issues.
@valleyforge
@gat
Ha! Shows how much I know. Scratch what I said above from the record.
I have not done a .22 conversion but have installed/swapped several gas blocks. Direct blow back for .22 makes a lot of sense.