I worked up a 243 load with 80 Berger's in the middle of the freezing winter. Load shot like a laser.
Once the outside temp went up just above 30 f, some of those bullets would not make it to the 200m target. 25% of them would disintegrate right after the 100m mark. And the groups at 100m were twice as big as when it was very cold.
I slowed down this load by 300 fps and groups shrank to what they were before, and no bullets blew up again.
This was in a 243win 8" twist 26" bbl.
Once the outside temp went up just above 30 f, some of those bullets would not make it to the 200m target. 25% of them would disintegrate right after the 100m mark. And the groups at 100m were twice as big as when it was very cold.
I slowed down this load by 300 fps and groups shrank to what they were before, and no bullets blew up again.
This was in a 243win 8" twist 26" bbl.