Is a Muslim sinful for inventing a defensive handmade device that could be used by gangs if the purpose of the invention is trade and abundant profit?

There is no objection to selling a patent for a weapon as long as it is not known that the buyer will use it for impermissible purposes, or if the buyer is at war with Islam and Muslims. Jurists have stipulated the prohibition of selling weapons to a combatant. It is advisable to sell the patent to an Islamic country.