I've been doing this for years and I have the shittiest arms around
but I do agree with the correlation between bodyweight and arms whilst there are exceptions like me on one end and the 200lbs 19 inch arm mesomorph78 on the other... I will have to be 300lbs to get 20 inchers
but I find concentrating on hammer curls, barbell curls, CGBPs etc... to help make up for me falling into the "grrr training arms is for girlie men trap" earlier on
Thats genetics bro , once past the beginer intermediate stage , curls wont do shit for arm growth.doing cleans,rows,chins heavy pressing will stimulate more growth in that area as long as diet is on song.
What are you weighing now man?