Myself I would choose the 8mm or the 7.62X54. Problem with the 7.62X54 ammo is that chances are you would have to order it, a lot of places won't have it on the shelf so to speak. The 8mm they might. I didn't mention the 303 simply because I am just not familiar with it at all. What I would do is if ordering ammo isn't your thing I would go to my local Walmart or gun shop and just see what they carry in stock.