When I first started load for the 243 Winchester in 1979 or so I used Surplus 4831, IMR4350, and WW785 with 105, and 80-grain bullets. The 243 liked the slow burning powders. At that time I was happy with the 243 Winchester as a varmint rifle and I started loading H414 with 80 grain bullets; a very accurate load.
This spring and summer I started developing 243 loads for deer hunting using 105 and 100 grain bullets. Slow burning Winchester Magnum Rife Powder better known as WMR proved to be outstanding. But with that in short supply I turned to H414 and 100-grain Nosler bullets based on other members recommendations. H414 easily produced loads with 100-grain bullet averaging 3009 fps. This is the load I settled on. I had loaded a ½ more safely, but to create a wider safety margin I backed off a little more.
This H414 velocity exceeded the velocity of factor Remington and Federal ammunition. Not only was it faster but more accurate.
Dave is right 760 (H414) is the Ball Powder answer to IMR4350.