The 204 is a good gopher cartridge but something to consider with it is the availability (or lack of availability) of 204 brass and the higher cost of it as compared to the ready availability and low cost of 223 brass. There is also a more plentiful selection of bullets for the 223.
The 204 burns the same amount of powder as the 223 but it is burning it through a smaller bore so barrel life will be a bit less than the 223.
I cannot see any reason for a fast twist for a gopher rifle, the most common bullet weights are 40 to 55 gr and a 1-10 or 1-12 will stabilize in either with no problem and probably have a slight accuracy edge.
drover
