It's not grease. BAR has it right in that it's a tar based sealer.

bob q, you contradict yourself in the first sentence of post #10. I'd suggest you have a good long look at the bolt and body locking lugs and recesses in your rifle/s. I've never seen an Enfield bolt without locking lugs. If you have one like that, I'd caution you about firing it! Working pressures are around 45,000 psi in .303 and 50,000 in 7.62 NATO. That's not exactly what I'd call low powered either.