a 100 yrs ago , they used kerosene , it worked just fine and does not have ammonia . Then they would wipe it down with a light oil .
If you google " Eds Red " it will give you Ed Harris's recipe for an all purpose gun cleaner that is cheap to make . I believe the problem with Hoppe's is if you leave a coating on the gun when finished . If you wipe it down afterwards and give it a light coat of oil there shouldn't be a problem . I used Hoppe's for over 50yrs . Today I use Safari Charlie and sometimes Kroil , works great , never had a problem on my new guns . Kroil recently had a great sale @ the factory , 2 large spray cans for the price of 1 . So for now I'm well stocked up .