If the strain screw is tight and the correct length, your next step is open it up and see how dirty it is inside, and is there a big "kink" in the mainspring? Do you have good reliable quick trigger return? That is often a problem as the "home gunsmiths" either clip a couple coils off or put in a 11 or 12 lb. return spring. It needs at least a 14 lb for reliable return.

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H Richard
SWCA1967 SWHF244