I am planning on buying a parts cleaner that has a recirculating pump.  What is a good safe solvent I can use.  I need low to no flammability.  I have seen Simple Green used to soak car parts in that came clean after a good brushing.  Is that a viable option for gun cleaning?  I am used to using Breakfree and Hoppe's no.9 solvent.  Any suggestions?

I've used Simple Green at 50-50 solution to water with good results. This is the industrial grade purchased at Auto-Zone, Not the pre-diluted spray bottle stuff. Works well but is
NOT for use on anodized aluminum (AR15 uppers &
Lowers for instance) as it removes the anodizing
over time. This idea comes from the gunsmithing video people AGI (I think,Sometimes) who use
it instead of solvents as it is more people
friendly/enviro friendly. Good shooting, Chuck