First you need to spell "BOOLIT!"
The 300 Lee is a good boolit. The RH is a fine gun.
Use WW metal, the clip on weights, not the stick on stuff. You can water drop from the mold or just air cool them. I water drop and let them sit a few days to harden.
Get some H110 and put 21.5 to 22 gr in your load. If weather is moderate a Fed 150 primer works great and the WW LP primer works fine. I do not use a magnum primer in mine. use them if it gets VERY cold.
Case tension on the boolit is important and Hornady dies work best for me. Use just enough crimp to fold the brass to the bottom of the crimp groove. Lee has small grooves so don't over do it.
You need to determine the diameter of the boolits to fit your throats by slugging he throats but I would say .452" would work. Try a .452" Lee push through size die and if you need larger, the die is dirt easy to lap out and cheap.
This load is accurate, will make it feel like a .44 mag and will go through any bear. Your velocity will be over 1150 and up to close to 1200 fps depending on barrel length.
Use a soft lube like Felix, stay away from crayon hard lubes.
You will find your own cast will be 100% better then bulk boolits like Magnus or Laser Cast and only LBT styles that you buy are as good.
Making your own will get you down to a dime a shot. That's 10 bears for a buck!