Boiling water is probably the best and safest way to remove real cosmoline from parts.
Cosmoline seems to have become a generic term for whatever grease a rifle comes packed in. The Springfields the CMP sold years ago (at least the ones I saw) were packed in nothing but good old automotive grease; I believe the CMP indicated it was automotive grease on their website at the time because so many questions were being asked about how to best clean them. I cleaned up a few of them by soaking the small parts in a bread pan in kerosene and wiping the stock with mineral spirits, which does no harm to the wood while removing the grease. I saw some Yugoslavian rebuilt 98ks that were also stored in automotive-type grease. Rifles so stored will sweat grease from the wood on a hot day for a long time after it's cleaned up.
