Yes, you have to work up the loads, watching for excess pressure signs, to make sure you are not over loading your rifle. And always use loads that you are comfortable with.
I'm looking at my note book and on Nov.14, 1990, with the temperature 45 degrees F., I chronographed five of my loads in my 243 Ruger 77, with 22 inch barrel. The chronograph was an Oehler 33, the load was 47 grains of Norma 205 with a 100 grain Sierra bullet. The velocity averaged 3094 fps.
I always interchanged the load of H4831 and Norma 205/Magnum powder, as I could never notice any difference in pressure between the two.
At the same time I had an European made 243 and 45 grains of H4831 or Norma 205 was maximum in it.
Since then I have loaded for three other 243 rifles and every one of them would easily take 46 grains of H4831 or N205, with a 100 grain bullet. Every one of my 243 rifles have given long case life, with no enlarging of the primer pockets to shorten their life.
My present 243 is the Marlin XL7 and it takes 46 grains with no sign, whatsoever, of excess pressure, with a 100 grain bullet and either H4831 or Norma 205.
I like the Norma powder better, because it is denser than H4831, so there is no, or very little, compression with the Norma powders.
And yes, the heavy loads do shoot the best.
Also, regarding the temperature, I make no allowance for temperature. I have been shooting quite a bit at the range this summer, with the temperature often over 30 degrees C, and I use the same hand loads, with every calibre, that I use in the winter.
If I was using handloads that stretched the primer pockets, I would slack off the load in hot weather, for sure. But I don't load heavy enough loads to worry about it.