How standard is this bluff?

[Sluss]

Pokerroom 50+4

Pretty tight table. CO has called a few raises with position and then folded the flop. I've only played 6 hands (and only two to the flop) hard and fast and have yet to show down a hand.

First hand of 75/150

Hero (t2700)
MP (t4200)
CO (t2600)
Button (t2600)
SB (t1635)
BB (t1265)


Preflop: Hero is UTG with A [img]/images/graemlins/heart.gif[/img]J [img]/images/graemlins/spade.gif[/img].
Hero raises to t400, MP folds,CO calls t400 , Button folds, SB fold, BB folds.

Flop: (t1025) 3 [img]/images/graemlins/club.gif[/img],K [img]/images/graemlins/heart.gif[/img]7 [img]/images/graemlins/heart.gif[/img] (2 players)
Hero bets t500, CO calls t500

Turn: (t2025) 4 [img]/images/graemlins/heart.gif[/img] (2 players)
Hero checks, CO bets 300, Hero raises all-in

Sure half his stack is in the middle but what can he call with here?