An outline of the BV-50...
It is designed to fight and kill Jedi Knights. It has already done so. Some of its information to fighting was gathered off of Xeth, actually! And then it cut off his leg.
It has an energy shield, like the destroyer droids of the Trade Federation. It reflects laser fire from standard firearms. Heavy weapons may breach the shield, lightsabers do.
It is loaded with weapons. Multiple mini-gun blasters so that it can target multiple foes, a cutting laser that is just plain lethal, and a disruption field that burns you when you get close.
And it can fly out of reach of lightsabers.
But Denzral is right, it is not invincible. Just incredibly hardy and well-equipped...
The field is '720' is it where.
Note, btw, that sabres do not penetrate the field per se, but you can just stab through it. This is not convenient and gives the BV a very high close combat defence score.
You guys are in an adjoining corridor.
"Look, what IS this droid thing you are talking about?" asks the Colonel.