R.Marshall,
If you already changed springs, you might check firing pin protrusion. Firing pins are sometimes damaged and replaced or sometimes "cleaned up"( meaning re-contoured, not actual cleaning), either could result in reduced protrusion. It is hard to ID a problem with out the rifle "in hand", some transitional actions were made with the new style firing pin that required the bolt to be fully closed or it wouldn't fire; it would have the two protrusions where the "Pin" part comes from the main body. The old firing pin wouldn't have this, it would be round here like a 93/94/95/96 action. If an old style firing pin was replaced with a new style one, the protrusions or maybe partially removed ones might interfere. This is also a traditional sign of excess headspace, but I did note you were using 6.5x57 ammo, and the chamber cast didn't indicate re-chambering to 256 Newton( a somewhat popular modification). If you have another Mod 98 Mauser, it might be instructive to test the rifle with another bolt and check the firing pin strike. If it is still too light, you might stack .004-.006" of shim material between the cartridge head and bolt face of the original bolt, and see if it closes w/o force.
Mike
