No5 Jungle Carbine

[RossM10]

(I'm definitely not sure, but this may be the predecessor of the mysterious XG 297 grease). This beeswax/mineral jelly combination repels both water and oil while preserving the wood.

XG-297 is mysterious as there is no record that this code was ever used.
XG-279 however has been mentioned before but there's nothing mysterious about it, it's plain regular automotive grease.
The relevant Defence Standard defines it as:
General purpose lubricant for automotive and artillery applications,
operated over the temperature range of minus 54°C to plus 105°C.

It is based on mineral oil with a metallic soap thickener. XG-279 is a UK designation, the Nato equivalent code for it is G-403.