When I'm shooting for fun or trying out a new load, I switch hands and shoot as many rounds left-handed and right. If I see or feel anything strange with either hand - like a bunch of close groups left handed but loose groups right handed - I know there's something wrong. Maybe it's me, maybe it's the load, maybe it's the gun, maybe it's the phase of the moon - something. Now, to be clear, I'm NOT saying I shoot as well left or right handed, what I am saying is, the groups I'm shooting from any given load should be about the same as any other given load with the same hand. If my trusty-tried-and-true 3.3gr. of Bullseye .38 is holding 4" @ 25yd. left-handed, and then a new 3.5gr. load of W244 is all over the target, I know "something" is wrong, somewhere.