Those are bogon attractors, for barrel break-in.
The bogon attractor will suck all the bogons out of the barrel, then you're good to go. All the BR guys are doing this now, I hear.
Can you use the attractor more than once? How many bogons are sucked to the attractor at a time? If you increase the angle of the barrel, will the attractor go too fast, come out too early, and cause the bogons to fall off? Can too many bogons really cause blindness?