Last gun show I went to, one of the local, licensed, reputable small mom and pop reloading companies sold 100 round baggies of ammo. These generally were mixed headstamp brass, no name bullets(some were their own cast) and were a few bucks cheaper than those they had in cardboard boxes, using new brass and name brand bullets. They also gave a discount for trading in brass. They had their name and ammo description on a paper tag on the baggie similar to what I use on my ammo boxes. They had bulk ammo in large Tupperware containers and would fill baggies and tag them as needed. They have been to the last several gun shows in the area and you constantly see folks at these shows carrying baggies of their ammo around. Most are repeat customers. I don't see why their ammo would be of any more risk than any other commercial ammo. If this was the case of the OP, then I would have no more fear of shooting them than WWB or Wolf ammo. Now if it was some Yea-whoo sellin' outta the trunk of their car is the parking lot, it would be a different story. If they were loaded using .38 special brass there is no need to shoot them first outta your .357. Odds are they will be fairly mild. I too am leary of shooting anyone's but my reloads in my firearms, but, all in all, I'm bettin' more folks have blown up guns using their own reloads than someone else's.