Two choices: change to a lighter spring or put more powder in it. You are using a minimum load, which is fine in my revolver, but in a semi-auto, you have to have enough energy to work the "machine."
I don't know how you are estimating the MV, but I load 3.0 HP38 and measure the MV from a 4" Model 66 with a chronograph, more like 690.

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Science plus Art