You don't have to swing harder with the X 27; I couldn't tell ya how many times I put the X 27 in the ground the first few times I used it
Got mine last spring and really working it through this fall - It's definitely the swing speed, but also have to test the wood at hand. I STILL am going through to ground even after 'dialing it back" and put more than a couple good nicks in it from the rocks that seem to grow the best here.