I have acquired a 1903 Greek rifle. It is very hard to open the bolt and compress the spring. My other 1903 operates much more easily. Could someone recommend a procedure to cure the problem,please. Thanks.

Disassemble the bolt and clean and lube everything. give that a shot first. then look for binding.

The primary extraction cam is located on the front of one of the bolt lugs and, along with the cocking cam, is the source of much of your problem. A little judicious cam-surface lapping on both cams and then applying molybdenum disulfide (moly-d) lubricant should make things go a LOT smoother.
Regards, Joe

Thanks for the quick responses. Bolt lift is much improved.
dave