Example: I have played 3 spells then cast {Grapeshot} which will deal 4 damage. If I play another grape shot will it deal 5 damage or 8
Copies aren't cast, they're just put on to the stack. After the first Grapeshot, your 'Storm Count' will be 4, so the second one will make four copies of itself.
I see. What about {Pyromancer Ascension} spell copies?
They're still just copies put on to the stack. Unless an effect says otherwise (the only two off the top of my head are {Isochron Scepter} and {Panoptic Mirror}), copies are always just placed on to the stack and are never cast, so they wont increase Storm count.
Also, think about it. If Pyro Ascension had you cast the copies, it'd just keep triggering itself over and over again.
Very true. I'm attempting to build a ur storm deck and want to learn the basics. I'm assuming the same will happen for {Shattering Spree}'s replicate cost
Yup, you got it. Whenever a Storm or Replicate trigger (yes, they ARE triggered abilities) resolves, you just put the required number of copies of the spell on to the stack. This is one way that you can destroy an {Chalice of the Void} with one counter on it; since your copy of {Shattering Spree} isn't cast, it doesn't trigger Chalice to be countered,
Cool thanks man