7x57 Mauser
One of the things about the 7x57 (and also 8x57 Mauser) is that factory ammunition made in North America tends to be underloaded.
In the case of the 7x57 Mauser, there were many Remington Rolling Block rifles made in 7x57, and putting a higher pressure cartridge into this weaker action (compared to say a Mauser 98) is asking for trouble. Therefore, American ammunition companies tend to keep the pressures lower in the 7x57 to avoid lawsuits.
In the 8x57 Mauser, American ammo companies tend to underload because the original 8x57 Mausers (and also some European sporting rifles) used a .318 bore diameter. Later the Germans reduced the weight of their 8mm bullet, going to a Spitzer shape, but increased the bore diameter to .323. This is the 8x57 JS, (or 8x57 IS as it is known by also) loading used since before WWI.
The difference in 8x57 loadings is well known and recognized in Europe, but many North American shooters do not know of it. Firing a .323 bullet in a .318 bore could raise pressures considerably, so to avoid law suits and such, our ammo manufacturers underload this round too.
Now, to get to one experience. I once bought an Interarms 7x57 Mauser with a Mannlicher stock, that was based on a Yugoslavian Mauser 98 action. It almost drove me up a wall, because the only thing it would shoot was 175 grain round nosed bullets. I wanted to use 154 grain Hornady Interlocks for big game, but was getting patterns rather than groups at 100 yards.
Checking several reloading manuals, all gave about the same loads. The rifle seemed to like one powder better, but still gave large groups. Finally, after carefully inspecting the cases, it dawned on me about the underloaded factory ammo. Because this was a 98 Mauser action, of modern manufacture, I started to gradually work up hotter loads, very carefully, small incremental increases, with VERY CAREFUL inspection of cases after each firing.
The groups started to tighten up, and at a load that was several grains over the maximum listed by the manuals, with no signs of pressure (measured case expansion, no cratered primers, etc.,) the 154 grain Hornadys grouped into less than one inch. All that it needed was to drive them a bit faster.
I am not recommending this to anyone, because there is no control of any reloaded components, no way to visually inspect any firearm used, or other factors. I am just giving an insight on one of my experiences with the 7x57.
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. I agree...if there is room in your safe why not pick a 7x57 ? If you change your mind it should not be hard to sell. 
