I think that due to Bellamy being on Skypiea, he learned how to make his arms work like the impact/reject dial and on a larger scale.
How? Just like how the impact/reject dial absorbs the blunt force of a strike, Bellamy may be able to turn his arm into a spring, absorb the blunt force, and release it on a larger scale and with no drawbacks. Also, if he possesses CoA, he would be much greater.
How? Just like how the impact/reject dial absorbs the blunt force of a strike, Bellamy may be able to turn his arm into a spring, absorb the blunt force, and release it on a larger scale and with no drawbacks. Also, if he possesses CoA, he would be much greater.