You and/or your wife are doing well.
IF! all squares on all targets are 1" x 1" compare each 3 consecutive shots at 200 to the 6 shots shown at 100. Comparing 3 to 3 shows the rifle is doing it's part.
As with a race car, driver consistency is vital. You mentioned that you were not "comfortable" at the bench. Things won't improve until you get comfortable.
The 270 Win has been my life long friend. I'll bend over backwards to help a shooter that shoots that cartridge. It's a weakness bordering on addiction. :roll eyes:
This is a long range shooting site. I'll come at it from that viewpoint.
I recommend getting away from the bench. Not far away, just to the ground.
Do the bipod thing with a good solid rear bag. Your rig has plenty of weight, I'm thinking and recoil with your stated load shouldn't bother either you or your wife.
If you are shooting unexpectedly high @ 200 it maybe inconsistent or too little shoulder pressure is a problem. However, my 270 Win has always impacted higher at 200 when zeroed at 100.
I'm shooting 140 anythings @ 3200. I'm surprised you can get your stated velocity with 4831. I could never reach 3000 with that stuff.
I'm betting your rifle is good for 1/2 the group size shown, for 3 shots. With proper practice you and your wife will be also.
I"m impressed that you get that much accuracy from SSTs. They haven't performed for me.
Pay attention to cheek weld, shoulder pressure, bipod loading if shooting from one, and trigger break.
Keep posting targets. They tell a story.
Oh, don't waste too much barrel life messing with loads. Get one that you like then stretch the distance.
Good luck and good shootin'