I usually put three rounds down my T3 to zero and find the last wanders off abit, not much but its noticable. Thats sport rifles for you I'm afraid. My T3 Varmint heavy barrel shoots great for ages! Thing is, how many bullets do you want to shoot at one deer?
three shots are the way to evaluate such a gun. remove the moderator and allow to cool.
at a push you could fire as many as you need but don't expect accuraccy to be spot on.
a stalking rifle should in my thoughts be zeroed to point of aim on a cold clean bore - unless there is a terrific difference with a fouled bore in the gun in question in which case it should be stored with a fouled bore in preperation of stalking.
When i check my zero nowadays i lay down using the bypod with a sandbag under the back of the stock, but not always, go back to 100 yards and fire 3 shots, if they are within 2" and 1" high, that is me done and go away happy. In the past i have tended to stay and have a few extra shots but found that i was getting the odd flyer, this is natural as the barrel heats up.
You have to ask yourself the question, do i really need a cloverleaf pattern?. This type of shooting is all well and good on the range or for competitions, but in the field on deer or fox in my mind is totally unecessary.
It is possible to get one that far out, dependant on how warm the barrel is but reckon it`s more likely to be 2-3" above the 2" grouping. Its a long time since i went and shot lots of bullets off to be honest since i decided that 3 bullets was enough.
You have to remember that when you get a flier you then tend put a certain amount of pressure onto yourself to correct it when all you are doing is making the situation worse when really there is nothing wrong.
Now i`m no expert on ballistics but i know enough to know when its down to me and the conditions rather than the ammo.
Mathematically the best way to check mean point of impact is to shoot a five shot group.
Three shots then let the barrel go cold then a further two shots. Thsi allows for most barrel temp variation while hunting.
As was mentioned earlier cold barrel zero is the one you need to know for hunting all the restis benchrest plinking
goodness if a rifle moves 6" you have a serious bedding problem, bad mounts/ scope or are an awfull shot. Not that i am accusing anyone i do not know of such sins !!!
Statistically your second two shots fired after cooling might only prove your hold was slightly different. Five shot groups for heavy barrels three for light and you wont go wrong- these must have the same hold and be fired consecutively