Hi. What are the consequences of fps adjuster rings? Are they advisable for settled springs? Also what are their alternatives at the hardware store?
They're fine, I used 15mm thickness on mine and got like 20fps boost. As for the consequences, I couldn't think of any other than you might need to compress your piston and spring for a bit to put on the cylinder head. Not a problem in o-ring type pistons, but if you use cup type piston then that would be more work than usual. More so if you have aftermarket springs which is usually longer than the standard springs.
Also, make sure that the outer diameter of the ring is flushed to the inner diameter of the piston catch. It would make the piston won't move much when cocked, therefore achieving smoother bolt operation. Better explained by novvy here :
Additionally, if the material of the ring isn't hard enough, then there might be some dents after a while. So you better get a steel rings or just make sure that the base of the spring is flat.