GMRS can work rather well
just depends on how much power you have (i believe you are allowed up to 50 watts)
whether mobil to mobil or mobil to base or base to base
i get 8 to 10 miles with portable to base
(but using a high gain antenna and not those garbage rubber ducks that come with the radio)
I can not comment directly on how using a Icom 221 is
However when i use a
HT i use the Icom T-90A
(if memory serves is the same power as the 221 but simply with far more frequency's on hand)
using the Icom T90A seems to work very well on GMRS
now for range base to base
i have gotten 45 to 50 miles
but then our repeater hear has got an antenna fairly high (50
ft or so) and has no other buildings or structures in its way
i have not used GMRS for the last few months
so perhaps is time to start using it again
hope it helped