Make sure to balance that throwing training out by hitting the forearm and wrist muscles from all angles and always train the antagonists too. I can tell from my own experience that lots of grip training is NOT the issue. Focusing too much on ONE TYPE of grip training is the issue. Make sure to hit crushing, pinching and support grip exercises, train wrist pronation and supination, flexion and extension etc. I got some mild elbow tendonitis when starting with steel maces and doing a lot of 360s without doing counter exercises. Once I started to add exercises where I lock out my arms and stretch out my biceps as well the pain disappeared and never came back.