Absolutely splendid load in nearly all .243s is:
Winchester or Remington case
Winchester or CCI primer
Hornady 87gr. BTHP
42.5 gr. of IMR 4350
seat the bullet so it is just barely, barely touching the rifling
Try 42grs. first and look for any pressure signs. If there are none, try the 42.5 gr. load
There shouldn't be any pressure problems with either of those two cases.
Many, many, many times I've shot this load into 3/4" or less at 100yds. out of at least a couple dozen different rifles. And I've dropped a trainload of deer and hogs with it in their tracks. Have seen other shooters do the same.
Enjoy !