Try seating further out.
10X is a very sooty powder. Some guns like that. Some don't.
greystones correct. Pay close attention to your shots. First three touching then scatters means your fouling out. Either copper or carbon can do this. With 10X my money would be on carbon.
Last three touching means the group could be settling down. Only way to find out is shoot more of that load before changing the charge weight. Different charge weights can create different levels of powder fouling in the bore altering point of impact. It can take a few shots to settle down. The dirtier the powder the more pronounced this phenomonon can be.
Frankly I would have rattled off those groups in 10 minutes or less with my guns.
If they can't run warm they can't run period.
I think barrel heat is highly overated in all but pencil barrels. It will erode the throat faster but I've never once seen it alter POI or cause scattered groups in varmint weight barrels. Changing bore fouling is to blame for that.JMO
Of course in the heat of summer I run them slower.