Re: reloading for .243
If you get/have the hornady manual you can find loads for both powders I believe. I know H414 is in there. I am currently shooting the 87gr. Hornady BTHP's in my 243 and pushing them with 40.7 grains of H414. I get just over 3000fps. I don't have my manual here, but I'm pretty sure that this is a max, or close to max load, so you should work up to it with your gun. It shoots very well out of my Remington 700 though. I can't tell you about the IMR powder, I've never tried it. Good luck, and load safe.