it' s possible you have a confused situation....

first, there is no such thing as a 8 X 57 JS The original 8 X 57 had a .318 diameter bullet and was known as a the 8X57 J

After the turn of the century the bullet diameter was changed to .323 and that cartridge was known as the 8 X 57 S

If you have a gun chambered for 8 X 57 J, you must not shoot 8X57 S ammo in it....

This needs to be checked out ASAP....