For a hunting rifle I normally test with a three shot group.
You need to know where the first shot from a clean cold barrel goes. With a .35 Whelen you should not need more ;-).
If I shoot more than one group I let the barrel cool off. The majority of the sporting rifles I shoot are not free floated and they do start to move around after heating up.
Once your barrel is ambient temperature see where your first shot from a cold dirty barrel goes. Some rifles shoot better with a fouled barrel.
What does clustered nicely mean?
When one of my rifles has vertical stringing it's normally because I'm not resting the forend or barrel on the same spot for each shot.
PS: At 100 degrees I would be sick and looking for some air conditioning.
