I picked up a new 300 win mag and was planning on trying a few types of ammo to see what it likes but none of the shops around me have had any in stock since before last December and I can't seem to find any online. My father in law reloads and offered to load some up for me if I can get the components. He has magnum primers for me and I have cases but need a little help deciding what bullets and powder to get. Main goal is to build an elk round and I'd like to be able to go out to 400yards with it. I've always shot factory winchester 180 gr accubonds but I can't find any accubonds in stock (only taken deer, no elk). I have some 180 gr gmx on order but have read I should go down a size to 165 with solid copper but I cant find any 165s in stock. Is that a valid concern with a magnum or mostly for 06 and .308? Anyone have any other recommendations? Powder supply also seems to be an issue for the magnums.