Controllability

I try to check the controllability of a system with 310 states. So using Matlab I've seen 3 different ways doing so.

rank(ctrb(...))=4 (I know ctrb should not be used for such a system, this one is only for comparing.)

sum(k)=310 after ctrbf (so fully controllable! I cannot believe this because it says 310 even if I reduce the inputs to 1)

rank(gram(sys,'c'))=103

The last one seems possible but how to know this after the first two? Is there another method I forgot to verify any of the results? Any other suggestions how to check systems with even more states?

using Matlab R2007b

Thanks