You need to find yourself a chronograph in order to aid you. It is the best way to figure whether changes to your loads really benefit the gun. Another huge benefit is if you can recover the fired bullet for inspection. Lastly, do the changes increase accuracy? Those are the three things that ultimately determine whether these changes benefit or hurt.
And, speaking of hurt. I agree with Mickey, plinking with loads of that magnitude are not very fun. To each his own, certainly not for me.