And it looks like the front part of this:
http://www.wgcshop.com/pcart/shopper...G18-24_cat_KSC Parts
I suspect that this is the KSC floating valve.
The part is broken at the stem. I have the front part with fins on my desk and the broken base still sitting inside my loading nozzle at the moment.
What caused the failure? Should I simply replace the part with a OEM KSC one or order the Firefly rocket valve?
For reference, I have a FMU G23F with stock valves, reinforced/stiffened recoil spring guide set, stock hammer spring. And a steel mag catch, if that makes a difference.