"Transfer of cash doesn't denote anything except you took money for something. If their gun blows up because of a bore obstruction that was already there...it won't matter."
Ah, but it does. Personal activities and injuries caused by you in the persuit of your hobbies may be covered under your homeowners policy; Personal Liability. However, if you receive any compensation whatever, the activity could be considered a business venture and would be excluded, as such.
Although I believe there is coverage under the standard ISO forms of insurance for this hobby exactly like fishing or golf, your policy may well be different and would need to be examined carefully for an exclusion, by a competent agent.
I personally do not reload for friends but on occasion at the range, will allow a person to shoot my gun (s) with my reloads for a few rounds. Over the years I have found that people do strange things with guns and you can never tell. Like my hunting buddy that loaned his 391 to a guy, got it back full of water grass and mud, without a word, just wiped off. The guy finally admitted that he dropped the 391 in a pond. Imagine giving this clown a box of reloads and the gun explodes full of mud.
Ed