I recently had a 1891 Argentine Mauser rebarreled to 257 Roberts. Gunsmith cautioned me not to shoot +P ammo in it. In my research of factory made 257 ammo, found Remington, Federal, Winchester and Hornady made 257 ammo. However, only Remington made a standard load. All the other manufacturers ammo seemed to be +P. Emailed Winchester Tech, questioning if their 257 ammo safe to shoot in my 1891 Argentine. Their answer was: "All our ammo safe to shoot in modern firearms made in USA." Made me wonder if they think 1891 is new and that Argentina is a part of USA.