A few corrections . S is not a bore size . The 05 conversion is not for the S ammo [ there are a very few original non-Turk 05 rifles with NO S stamp and a rear sight with no grinding and still sighted for P-88 ammo ] , just for the stripper clip ammo pack . The Czechs never made any .318 barrels for the Turks . The Czech's supplied several barrel types to the Turks , NOS German barrels of .321 or .323 , new made .323 barrels for 88's and .323 model 93 barrels that the Turks turned down to fit 88's . The small bore Czech made barrels when to South America and were made to the old civilian specs of .316 +/- , never to Turkey . Lowe made ALL of their Gew88's in under 14 months , very early in the production of 88's , so Yes all of their original barrels are the early .321 thin type . To answer the original question about shooting , any US made ammo with a .321 dia bullet is fine in the original barrel rifles and will shoot well . It is in the later German .323+ barrels that it does not shoot well .