According to Handloads.com ballistic calculator, you should be good past 500 yards if you're getting those 40 grain bullets to 3900fps out of the barrel and you can make the shots..
Over 2100fps and almost 400ft/lbs of energy at 500 yards, at 65 degrees Fahrenheit, sea level. That's about 100ft-lbs energy more than .22WMR makes at the muzzle, almost 100fps faster, with the same weight bullet, and the .204 has an advantage on sectional density. People hunt yotes with 22WMR all the time. I think with the .204, the wind is more of a threat to your shot, than running out of 'juice' at ethical hunting ranges.
Just my $.02