In my current grenade, the brass tube was stuck in there, so I drilled a hole into the side of the tube and filled the cavity with like... water or vinegar or something, I forget, to saturate anything in there. I drilled the hole bigger and washed out anything in there, some little rings came out and some flakes of rust but that was it. I think in the "inert" process it was emptied but I wanted to make sure.