NitroX,

How long and how many metres would it take before the
buffalo drops? "

It depends. I have had buffalo drop dead immediately from a heart
shot and other try to run.

It also depends on whether the heart is full or empty when the bullet hits.
It makes a big difference to the effect.

Any heart shot with a 6.5 will kill the buff but you may have to follow it up quite a long
way if it runs.

Hope this helps

500 Nitro