This is a common problem if you install a trigger for a commercial 98 on a military 98. Military 98s have a notch in the bottom of the cocking piece to allow the sear to return to rest after a shot, commercial 98s don't. So what happens is a commercial 98 trigger's sear resets in that notch after the shot, getting caught in the notch in the cocking piece. Flat bottomed cocking pieces do not allow this because the sear doesn't rise far enough to reset.
So try this: clear the rifle, then dry fire it. Lift the bolt handle with the trigger pulled. See if this reduces the effort required. If it does, then you either replace the trigger or the cocking piece. Simple.
If the bolt lift is still hard, someone may have overheated the bolt when forging or replacing the bolt handle. If this is the case, Csenit can be used to re-harden the cam surfaces.