Gew .88 s

Question
I have a Gewehr 88/S rifle,also called Gew .88, that was given to me by a family member and I am wondering about what places might I be able to find the ammunition for it and how much I can expect to sell the gun for. P.S. for those who don't know the "s" symbol Indicates a rifle with a newly made (not re-rifled) 揨?barrel with the chamber bored out to accept the larger diameter (8.22mm as opposed to 8.1mm) S-Patrone ammunition. Modification dates from 1903.  

Answer
Hello Dave,Your Gew 88 was orginaly chambered for the the 8x57J cartridge with a bullet Dia. of .318",and a maximum chamber pressure of 45,000 c.u.p. If it was re-barreled to 8x57JS,the standard bullet dia. for this cartridge is .323 and the maximum chamber pressure is 50,000c.u.p. U.S. Ammo Manufactures load the 8x57JS(Mauser)to a maximum chamber pressure of 37,000 c.u.p. and a M.V. of around 2325 F.P.S.
with a 170 gr. bullet.Remington and Winchester both load the
8x57 and it can be found at most ammo dealers.It is not recommended that you fire the ammo loaded in Europe,as it is MUCH Stronger,and the older Gew 88 may not be able to handle the pressure.But most of all BEFORE you fire anything
in it, have a good gunsmith check it out and slug the barrel
to find out the proper grove diameter.The 8x57mauser is a
good cartridge,I have had a couple of Mod.98s and I have a Remington Mod. 700 Classic in 8x57 Mauser,I have to hand load my ammo to get its potential effectiveness.I hope I have been of some help.