I have taken game up to Red Stag and wild horses in size with the 7x57 as well as the usual stuff and it never lacked anything, once I used the appropriate bullet to the game hunted but that same can be said for anything else.
My loading over the last 35 years with this cartridge includes 25 bullets and 13 powders and it is most difficult to find a bad combination for deer sized animals and only when they go over 500 pounds, "may" some additional testing be required with heavier bullets.
I don't really need heavier bullets. I just like to shoot the gun. I'm going to take stock of brass tonight and tomorrow and start working up a load or two. Accuracy is what I'm really after. Like you said, deer are pretty easy to kill with shot placement and the right bullets.
