Tossing the shotgun into the barrel from some distance away "should be " against the rules.
I'm really surprised they allow that, and don't call a violation just because you happen to make a basket in this game of firearm basketball.
I see no issue with tossing a firearm into a dump bucket or onto a safe table. As a competitor it's a risk because things like this happen. From a safety stand point Its safe as long as he isnt throwing a sig. You definitely wouldnt like Run N guns where you are constantly getting swept by other people rifles.