Modded FN SPR A5M - reducing fps

Hi all,

I recently had my SPR chrono'd at my local site and it shot 523fps using a 0.2 (site limit is 500fps). The mods are as follows:

AA teflon cylinder
AA 45deg piston
AA M150
AA steel sears/spring guide stopper
PPS ball bearing spring guide
Prommy 6.03, 433mm
ML delta bucking, 80deg

Bearing in mind the rifle has only had around 300 rounds put through it since the spring was replaced, can I expect the fps to drop enough as the spring beds in? Or should I go about cutting/replacing the spring? I've read the cutting the spring is the easiest way to reduce fps but can lead to rattling issues. I'm concerned that using an M145 may drop the fps lower than I need (I'm looking for as close to 500 as possible). Failing that, would some sort of nozzle brake setup work?

Thanks in advance,
Duncan :shot: