Personally I'd remove the gas block, measure the hole in it (from gas port), get a wee plug made up and press into it and drill hole 1/2 the size and test.
Work it up with jet drills till you get what you want.
The can will add bolt speed to it also so want it to operate just ok with no can on, then with can it will be sweeeeeeeet.
SSS spring is Superior Shooting Solutions
I think its a flat coil spring you can cut to suit
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