Knew a fellow who did dabble in used parts, but not for guns. Told me he had a customer complain that several of the parts he sold them broke or fail shortly after installation. Trying to do the right thing, he asked the seller to return the part. The after he got them asked the customer to take a picture of the original broken or failed part. The customer could not do it. Later the customer admitted that the part was not broken after all just looking for a free part and being a bit of a dirt bag. Customer had to admit his "mistake" because the seller was going to a show where the broken item was going to be in plain view. As a end result the seller put him on a list of people he would not deal with and a couple other parts dealers did the same. Hard to find parts for your 75 year old tractor when all the parts sellers and junkyards tell you to pound sand.