Breech plug lube?

[GM54-120]

Nickel is for SS. It also is rated for higher temps than copper based.

You can even buy Teflon tape with nickel added for SS use.
https://cleanfit.com/stainless_steel_pipe_thread_seal_tape_70891.shtmlComposition: 90% PTFE/10% nickel

 

[WV Hunter]

Over 30+ years I've been ML hunting, I used only 2 things... Knight breech plug grease or teflon tape. Both have worked fine. Most of my rifles I use tape with no issues. A couple rifles I have - they have a tight fitting plug, so tape doesn't work as well (gets messed up on install) so I use grease.