I've read all of your posts on this rifle, but I'm not sure exactly what all you've already tried.
I would free-float the barrel and fully bed the action before I shot it any more. It sounds like the heating is causing some shifting of the action in the stock.
Is the third shot always in the same place?
Don
Yes, it does not matter what I do free float pressure point, it will keep putting the shot about 3 inches away on the right, it always does that does not matter what I am doing.
I had the same thing happen to me with my Ruger .257 Roberts using 100 gr. bullets with WW760 powder. Other combos worked great. You may be trying too hard to get a particular bullet or powder to shoot that the rifle just flat out doesn't like. Try another bullet, or bullet weight and see what happens.
I tried all the usual remedies, then bought a take-off barrel my gunsmith found and had it installed.
Problem solved.
My Model 70 is similar; first two go into a half-inch at 100 yards, third one is 3/4" lower and an inch to the right of the other two. I try not to miss with the first one, seldom shoot a third.
Tom
Don�t overlook the scope!
Hermann
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I had rifle that did the same. It was a full length stock and the bedding was poor. The barrel was very light and my remedy is that I am having a stiffer barrel full length glassed from chamber to muzzle. I hope it works.
It is important to me to be able to shot up to five shot accurately in a short space of time as I frequently have the need to kill a roe doe and twin kids at heel. If another female presents intself four deer within one minute is not uncommon. Hence I need a rifle that shoot true with a warm barrel.