"...Issued Enfield rifles were completely dissembled once per year..." Hi. Maybe when they were front line issue in some other military. No offense, Ed, but not once, during 6 years in the Queen's Service, as the TrgO then CO of a CF Army Cadet Corps were any of the 20 No. 4's or the 20 No. 7's or 20 FNC1A1's, on my MIU, completely dissembled. Inspected by the CF Reg Force weapons techs, but nothing else.
Prior to taking command, the CO decided to do an excessive cleaning of 'em, without keeping the bolt heads separated by S/N. Took the Reg Force Weapons techs, hours to sort it out with headspace guages. Go and No-Go only. The 'Field' wasn't used.
Not done to CF Militia weapons(C1A1's, Sterling SMG's, .30 and .50 Brownings) either.
"...know more about the Enfield rifle..." Start here.
http://www.enfieldrifles.ca/main.htm
Then here.
http://www.303british.com/
Any cosmoline will be long gone. Assorted oily gunk, not so much. A full bolt disassemly isn't required for that.
Always check the headspace on any Lee-Enfield. Especially if Century had anything to do with it. When they had a shop in Canada, they assembled thousands of No. 1's and No. 4's out of parts bins with zero QC. Not even checking headspace to ensure the rifles were safe to shoot. Fixing bad headspace on either model isn't hard, but you need the right bolt head to test with proper headspace guages. More of an issue with a No. 1 because the bolt heads are not number stamped like No. 4 bolt heads. You need a handful, at $12.90US each from Gunparts, to try with the guages until you find one that gives safe headspace. Same price for a numbered No. 4 bolt head(0 to 3 only.), but just going up one number doesn't guarantee anything. Especially if you have a #2 or #3 bolt head. Gunparts, currently only has 0's and 1's. They're not the only supplier though. No. 4 bolt heads run $20ish Cdn, up here.
"...CGN member "GAIRLOCHIAN"..." Saw that, but the name doesn't appear on a UN search. Not being argumentative in the least. Just saying.
"...strip my rifles down..." Not a bad thing to be sure, but you don't need to completely strip the bolt. Bolt head off and a bath in a container of solvent will do.