I've seen the supply end. For example, a manufacturer may sell direct with terms like "refund only if never modified or installed on a gun", but if Brownells forwards a fitted and non-resellable return for credit, the vendor will eat it or stop selling through Brownells. This is also the reason may vendors have more generous return policies if you buy on Amazon instead of direct.bownells has gone above and beyound for customer service. i had a tool set they could not get individual parts for. Sent me a complete new kit.
Take returns no problem. Im sure like any manufacture/vendor they will have some stuff that does not play well with others.
I saw one case where the buyer wanted an unusual combination of parts requiring two products, that would leave 50% of parts left over. The manufacturer said "no". A few weeks later they got a Brownell's return of the leftover parts from someone doing exactly what the factory said "no" to, and had to issue Brownells full credit for the return.