Jason Bowles joined us Wednesday on "TMZ Live" to clarify a few things he said earlier in the day -- the most important of which being his suggestion sabotage might've been at play here ... and that someone slipped a live bullet in a dummy rounds box on purpose.

We pressed him on that, asking what evidence -- if any -- he and/or his partners had to make a claim like that ... and Bowles seems to take a somewhat softer stance here.

Watch ... he explains they don't have a smoking gun, per se, and aren't pointing the finger at one person -- the possibility itself is there -- clear in the fact that a live round somehow made its way into a case that presumably only carried dummies, which are considered safe.

Of course, we also had to ask why the ammo was just out in the open if the weapons themselves were being guarded -- and Bowles has an explanation ... which makes sense.

He makes the point that dummies aren't dangerous, and don't necessarily need to be under a watchful eye at all times -- especially if no one is expecting a live round to enter the situation ... which he says is the case here. Namely, he's saying Hannah had no knowledge whatsoever of real bullets being anywhere near the set.

That leads to the final puzzling mystery of ... if target practice was, indeed, going down as frequently as we've heard it was during off-hours, how is it she didn't hear it or hear about it???

Bowles response is this ... if that was actually happening, it must've been taking place very far away from where she ever was, because he's firm that Hannah knows nothing about it.