Leo has a point-- to a degree, how large we can develop muscles is largely predetermined genetically. Look at your parents' legs to see some idea. If you have 'high insertions', that is, your Gastrocnemis very quickly ties into the achilles/soleus bundle, then you will pretty much always have that condition to fight against-- although as I said earlier, stretching and massive overloading of the muscles can help.

With regard to weight training, you need to go super heavy and perform the movement SLOWLY and through the full range. If you think about it, your calf muscles are already insanely strong-- just one of them can easily lift your own body weight (as seen if you do a single leg calf raise). So, you can overload the muscles' capacity by lifting many times your body weight in standing calf raises, and by going very heavy in seated calf raises.

You can always get calf implants, too