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Nope, but you have to go by weight not volume. The process works buy pulling moisture, turning it into a brine and soaking back in. The size of the salt does not make a huge difference. Consider Corning Beef was named because the salt was the size of Corn Kernels. Use it...JJ
The size of the salt grains does not really matter for either wet brining or dry curing (unless of course it is in blocks!). When making a wet brine it can take a little longer to dissolve and when using it as a dry cure it will quite quickly draw water from the pork and make its own brine.
As JJ says the important factor is to carefully calculate the amount of salt and cure needed and weigh them. Do not rely on volume measures or the grain size can make a BIG difference. When measuring out the curing salt (Cure #1 ?) you should really use scales that are accurate to at least one decimal place.