I usually use .243 remington core lokt 100grn soft point for deer and .243 remi accutip v 75grn ballistic for fox.
My rifle is zeroed in using the accutip 75grn to shoot 1.5" high @ 100yrds, about 3/4" group, barrel cold.
I don't charge my scope settings when using the core lokt just allow for drop.
I ran out of the core lokt 100grn and so had my gunsmith, but I managed to get hold of a box of federal 100grn soft point.
As I hadn't used these before I decided to check them out on a target @ 100yds to see how they performed.
I started off with the remi accutip 75grn and fired 3 shots and they grouped 3/4" at 1.5" high of centre (Spot on)
I then switched to the federal 100grn and fire 3 shots and they grouped 3/4" at 1/2" high of centre. (which is as expected)
This is the point when I should have packed it in, but no I decided to shoot 4 more rounds using the federals (barrel warm,weather warm)
The first shot hit the centre, the second 1" low, the third 2" low, the fourth grouped at 2" low.
I then decided to use the accutip 75grn because I know these usually shoot 1.5" high, 2 shots grouped at 3" high.
Now I know its to do with the barrel temp and I should have let things cool down, deer stalking/foxing is all about that first cold shot.
But why if the federal 100grn started to drop lower didn't the accutip do the same, they actually shot 1.5" higher.
I then waited 30 mins with my gun in the shaded with bolt open then shot 2 shots using the accutip 75grn and they grouped 1.5" high.
Luckily I never touched my scope settings at any time, just a bit strange. ( I'm fairly new to rifles so go easy)