Home made bore cleaner

I worked with a Bench Rest Shooter many years ago and I learned from him, the shooter made their own bore cleaning solution.
They used Kroil & GM's Top Engine Cleaner in a 1:1 or 2:1 ratio. GM no longer makes that particular cleaner, so does anyone know what could or would work in its place?

I can tell you, it would not contain any Ammonia. No Bench Rest Shooter would ever put ammonia in the bore of any rifle.

Dawn dish soap and water.

Did the bench rest shooter you worked with shoot bench rest muzzleloaders using black powder? Petroleum cleaners tend to cause additional fouling build-up when used with black powder. A good nylon brush and a good detergent may do what you want.