Yeah...you should have loctite'd it...LOL
Check the inner cylinder wall too...if the piston head went sideways on you there's a good chance the screw scratched that up.
The Modify polycarbonate bearing piston head is a good one. It's a good thing to match the brand of the piston with the piston head...to see that the total length of the piston/piston head is the correct length (i.e. not too long or short).
Best of luck