I've got two 7x57 rifles, both sporterized surplus. 1 is a Mexican small-ring 98 with a 24" barrel. The other is a Dominican Republic carbine with a 20" barrel. The DR rifle is the most accurate non-AR rifle I have even though I bought it as a donor. I then made the mistake of shooting it. I threw a cheap Centerpoint 4-16x50 scope on it, got it sighted in and it was shooting 1.5" 5-shot groups with cheap PPU 139 grain rounds. Handloads do better. With 120 gr NBTs, I shot a 1.5" 25-round group. I do wish it had another 4" on the barrel though. The Mexican rifle isn't quite that accurate but it's good enough for deer out to about 300 yards.
If I didn't have those, I'd probably have a 7mm-08. I am going to be building their big brother, a 280 Rem AI on a Savage 110 action hopefully before the end of the year.
I really like the 57mm case rounds. I've got a 257 Roberts, the aforementioned 7x57, a slew of 8x57 in both military and sporter dress, and I'm also having a 6mm Rem built on a 1909 Argentine action. I thought about a 5.6x57 RWS, but that seems waaaaay too overbore for me. I'd like to have the throat last longer than 50 rounds.
I'm torn as to whether to build a 6.5x55 Swede or a 6.5x57 (or 6.5x257 rob) just to continue the 57mm theme. And a 9.3x57 simply to complete things even thought it would be almost useless where I live.
Matt