Actually I never even thought of that, I have some Hoppes No.9 bore solvent in a bottle, shoulda tried that.
Did my 50/50 ATF/Acetone cocktail earlier, let it soak in for a good while, then remembered that I need to buy a new bit of RHS to use as the handle on my action wrench, just in time for Bunnings and Masters to be closed. D**ks. Looks like it's going to get to sit overnight now.