Cheap fixes first--is your rifle's stock in good shape. Recoil lugs in old gunstocks can split, be oil soaked, uneven compression of the wood underneath the receiver, etc. This can cause patterns like a pepperoni pizza. Check to see if the receiver surfaces around the action screws mates well with the trigger guard. Corroded and rough surfaces in these mating areas can cause problems.
Second, is your barrel free floated or do you still have the handguards, barrel bands, etc. on it. If it is free floated, then use the dollar bill or index card method of checking to make sure that the barrel is not touching the stock. However, your barrel might do better as some do with a pad of cork etc. right at the tip of the forestock to put some upward pressure on it. If your rifle still has the handguard, barrel bands, etc. make sure that they are tightened to the proper specification (usually, not always, hand tight).
Last, but not least, check the barrel crown--even small nicks can affect accuracy. Does your barrel have pitting--this can make a barrel foul quicker which affects accuracy. If your barrel is worn, then consider using flat based bullets rather than boattail in fmj. And of course, make sure that your sights are properly attached whether iron or scope.
Do one cheap fix at a time and evaluate improvements using the same ammunition--Prvi Partisan has some very good ammo for this. With a little work unless the barrel is very worn, most guns can be made to shoot within military specifications, usually about 3-4 inches at 100 yards and perhaps a bit better specifically working up handloads tailoring the bullet to the bore etc.
PS, if you want a Swede--Samco had some worn swede barrelled actions for a reasonable price--Swedes are easy to rebarrel and relatively cheap spare parts such a trigger guards are around at places like Numrich and Sarco. Fleabay often has small ring mauser stocks for a cheap price. Bought a T38 Swede stock for $10 with a split toe--easy fix. As usual, YMMV.
