OK, have tested my first go at home loading the 243 today.
I had made up 5 batches of ammo, basic components were:
Hornady Vmax 75 Grain Bullet
Hodgdon 414 Powder
The first load started at 42 grains of powder and each batch increased by one grain up to 46 grains, the results of a 4 shot group for each are below. Shots taken prone at 100 yards of a Harris bipod and no bag.
(Note, the squares are one inch)
42 Grain Powder, the final shot to the right was entirely my fault and not down to the load, as soon as I pulled the trigger I knew it was a fluffed shot.
43 Grain, the top shot may be down to me so possibly should be discounted.
44 Grain, getting better.
45 Grain, seem to me to be the best.
46 Grain, things start to open up a little.
All cases looked fine after shooting and I think I am pretty pleased with the results of my first attempt at loading. 45 grain look to me to be the best.