90% plus of shooting is mental. consistency is about concentration.
Do not fire a shot without concentrating on the fundamentals. Forget get the group, for get the last shot, the last shot is history.
You say your first group is good, fine. The same group should be the same.
You have a zero. You know where the bullet is suppose to go. Good, no put up your spotting scope, don't look at the target until you are through shooting.
Take a note book and write down everything that's happening. Call your shots. Write in your note book the call. Example #1, black, 3 oclock. #2 in the white high, 12 oclock, etc.
If you are going to shoot a 80 shot match, DONT. Instead, shoot 80 one shot matches.
Concentrate on one shot as if its the only one you are going to get, With enough practice and concentration you will find yourself automatically concentrating on one shot. Its a habit you can develop.
To give you an example, I've fired a lot of HP and 1000 yard matches over the years. On slow fire at 600 and in 1000 yard matches I always seem to get a good shot the first one out. I know what I'm suppose to do. I know my zero, I check the wind and temp. Take a second look in the scope to make sure nothing changed (or correct if it does) and let the round go. I get sloppy and start chasing spotters instead on forgetting the last round (which is history) and concentrating on the conditions of the round I'm shooting now.
I"ve always shoot better scores if after each shot, I come back to my windage zero, check the scope, seen what I need and put it on the rifle, fire then put the zero windage back on.
I'm in fact firing 20 one shot matches instead of one 20 shot matches.
The same applies to practice or plinking at 100 yards.
You can only shoot one round at a time. Only worry about that round. Looking at history (the last shots) will effect your next shots because you are thinking about the last shot(s) instead of concentrating on the present shot.
When I coached, I would never let my (newer)shooters see their data book, I kept it for them. They gave me the call and I would plot it. Nor did I let them have a spotting scope on the line. After they completed the string I might or might not tell them the score. After the match back at the motel room and the equipment is put away, I would set down with them and go over their score book, studying every shot. That's when you can think about History.
The time to look at groups is at the end of the shooting session. Then look at the group and see if you can spot the calls you noted in your note book.
Unrelated: Never underestimate the value of a data or note book. Write down everything.
each of these boolits will kill a deer, speed doesn't kill, shot placement does....
) many times that one needs to forget about the target. It's merely a recording device that records how well you executed the fundamentals for each shot.