A question to the experts

[MEHavey]

My thought (knowing nothing than given above) and assuming no cleaning between strings:

The first shot is low due to a cool barrel unwarped from any undue stock contact. It hits where it hits.

The succeeding shots in the string are now coming from a warm(er) barrel which has warped (ever-so-slightly) into some tip-pressure from the stock -- and hits consistantly/slightly higher than the first.

Test #1: Get some chrono readings. I wager the first shot is not that much different velocity-wise than the rest.

Test #2: Fire 4 strings using 2 targets: Left target for 1st shots, right target for all succeeding shots. I'll wager again you'll have two different -- but "ok" -- groups.

Test #3: Fire 5 rounds -- but 10 minutes apart. I'll (lastly) wager that you'll have one group.