I apologize if someone already thought of this but: I 'm setting up the Hornady lock ringed dies on the lee classic and one has the allen head lined up towards the center and no way to tighten it. Looking at the Lee lock ringed dies I have I I turned in the allen head screw till the ring just turned, installed a HF #212 O-ring under the Hornady dies and tightened them down onto the turret. They hold tight!
Cycled about 50 round and no loosening! I hope this is helpful.