close to harvest?

Ok so i think i know what everyone is going to say but my pistols are turning red. Doesn't seem like the buds are really big enough and wont be for some time. Is there a rule of thumb on how long it takes after they start turning or is it like everything else and based on strain??

Go by the Trichromes, the hairs will start turning brown towards the last half, they could have weeks to go still.

Harvest at your desired trich level.