Before you get too excited, 1. what is the current chambering? 2. are they milsurp actions, if so what was the original military chambering? 3. refer to a reliable! (original specs were for a .470" rim dia in the 7.92x57 IS, manufacturers have changed it to .473", Wiki is not your friend) source for cartridge rim dimensions, compare original with current chambering 4. measure your brass to ensure it is correct, do not trust the manufacturer, particularly if it is S&B who does not cut the extractor cut deep enough on their brass in many cartridges 5. check and see if your bolt is numbered to your receiver, do not assume the bolt matches the receiver 6. aftermarket extractors frequently are the problem 7. bend the extractor in between the rear and the collar, which moves the claw away from the boltface guide boss and test feeding with a properly dimensioned cartridge
Do not remove any metal from the bolt face guide boss or feed rails until you know for certain where the problem lies.
Most '98's will feed .473" brass easily, occasionally you will find an action made in the '20's or '30's that was made so precise that it will not accept the increased rim dia.
