Brake cleaner is nothing more than a degreaser made for cleaning steel and aluminum. There's no big difference between it and say Gun Scrubber, other than price. Gun Scubber is ridiculously expensive.
If one product is rated as suitable for cleaning and degreasing steel or aluminum parts on your car, it's not going to dissolve the steel or aluminum parts on your handgun.
The caveat to that is polymer parts -- you have to make certain what you're using isn't going to affect polymer.
But, since I don't own any polymer handguns, it's not a consideration for me.
"gun solvent in a parts cleaner."
Fact - the majority of "gun solvents" are composed primarily of mineral spirits.
Fact - Automotive parts cleaners of the type maintained by Safety Kleen, Diamond, etc., or available through a multitude of auto parts stores, are filled with... mineral spirits.
Ed's Red, a highly regarded "make at home" cleaning solution, uses mineral spirits as one of its constituent parts.
The PRIMARY difference between a quart of Ed's Red and a 4 ounce bottle of most "gun" cleaning solutions?
The quart of Ed's Red is a cheaper. A LOT cheaper.
The point I'm making here is that just because something has "gun" on the label doen't make it super special and full of magical properties.
The ONLY magic in most such products is that they magically part you from your money and convey it to the manufacturer, who realizes astronomical profit margins, often 300% or more.
And all because people have this weird notion that if they're going to clean/maintain their gun, any product they use MUST have the word "gun" on the label.