With regards to bullets heavier than 300 grains I would suggest 4227, when you start get this heavy it is not about max velocity.

With the 350gr I would start with 4198 even in your barrel length, if it to dirty then go 4227.

I use 4198 with good results above 340 grain with my 460s though dont recall if I shoot any through the shorter barrels.

I will tell you the heavier bullets do have substantially more muzzle flip than lighter bullets compared out of shorter barrels.

For lead I like Beartooth bullets stuff- consistant

be safe
Ruggy