Jerking the trigger occasionally with semi autos but not with a revolver.

I recently shot four PPC matches on the same evening.  60 rounds each.

Round 1:  Pistol: 686, Ammo: Bunnyfart 38s, Score 560s, generally centered on the targets.  All shots fired DA
Round 2:  Pistol: Sig M11A1, Ammo: Low power 9mm, Score: 520s generally centered but with several shots low and left on the target.  Starting shots fired DA.
Round 3:  Pistol: Sig P320, Ammo: Same low power 9mm, Score:  490s, shots generally centered but with even more shots low and left on the target.  3 shots outside the 7 ring but still in the black.
Round 4:  Pistol: Same 686 as round 1 and same ammo.  Score 540s, generally centered on the targets.  No low/left 7 o'clock shots.  All shots fired DA

I generally do not have trouble flinching, jerking, etc, and can generally call the very infrequent shot where it happens.  I did not notice anything worth calling when shooting.
I did not have any 7 o'clock shots with the revolver.

Can you recommend specific dry or live fire drills to confirm or correct trigger jerking?

Thanks!

When you dry fire does the muzzle pull down on your autos?  Sounds like you have trained yourself to a heavy DA trigger and when you move to a lighter trigger you are applying the same pressures and pulling the muzzle down.  You need to practice more with your autos is what it sounds like.  This is not uncommon for someone to move from a pistol with a heavy trigger.  You have trained your mind and hand to press the trigger a certain way translating to you applying that to all pistols.  Some people can move between different pistols and be fine some cannot and require more practice.

Dry fire! Dry fire! Dry fire! Watch that front sight.

Again FPNI

I have a tendency to occasionally shoot the 320 low and left also. I don't do it with Glock 19, M&P 2.0, or CZ sp-01.

A good DA revolver trigger is smooth and easy to apply consistent pressure to the trigger. A striker fired gun is going to stack a bit through the trigger press as you make contact with different parts of the action which will make the pressure you need to apply vary and the SA trigger in a DA/SA gun is going to have a slight take-up and a short, hopefully crisp, break. 

The shorter the trigger travel is, the less feedback we have to judge each part of the press, and the more the pressure needed to move past each point in the trigger stroke varies, the less we're able to be consistent from shot to shot. 

How to master the variations without feedback before the shot or making the trigger extremely light?

Without seeing you shoot, I'd say that the two things that you can control the most are also the most beneficial.

You're never going to get just enough trigger pressure to break the shot without moving the gun on every shot, it's a wasted effort. What you need to do is grip the gun harder and press the trigger consistently no matter what feedback you have. 

You might think you're gripping hard enough, but you can do more and you might think that you're being smooth and consistent in the trigger, but you can do better.

It's just that simple but it isn't that easy.

FPNI

It was amazing what I saw myself doing when I started really doing and focusing on dry fire.

For warm ups I start by just pulling the trigger about fifty times starting slow at first and gaining speed until the last ten are pretty fast while making sure my front sight post moves as little as possible

I take the "Operation" approach. If the light disappears between the front sight and the left or right of the rear sight I fail. if the top of the front sight breaks the plain if the rear sight I fail.

The one gun I shoot low left with if I am not really focused is my 9mm S&W Shield.

I don't do it nearly as often with my full size M&P's, or AT ALL  with my 1911's.

My Shield has the heaviest trigger of the bunch. That, coupled with my large hands, and the guns small size. It's very easy for me to start pulling them low and left if I am not 100% paying attention to the basics. I really catch myself doing it when moving to the Shield at the range after I have been shooting 1911's. It takes me a mag or two to "settle down" with the Shield.

Thank you for the helpful replies.
The revolver was worked on in its past and has a smooth but long pull.  Both Sigs are stock.  
My guess is that I did have some jerking that I didn't notice in an effort to make shots on time, even though I haven't had this problem show up with other revolvers or autos.

Sounds like I need to shoot these two pistols some more and dry fire the M11A1 a lot!

Thanks again.

J.

Experimentation w/grip size & finger placement has been the greatest help for me.