I`ve recently had a "fiddle" with this model too.
I`ve long suspected the Marushin Bolt head and extractor claw as being a big problem ...they seem to work fine when a kit is new but quickly wear and performance drops off .
so I did this ( yes I know I should be shot for lack of cleaning this before doing photos

)
recognise the MGC M16 bolt head here ?

and with it extended

I used a brass tube to allow the firing pin part to sit centrally , one hex screw holds the brass tube and the other provides a guide for the pin ( where it narrows)


of course this means I use the MGC CP cartridges now , however as they dont fit so well into the Marushin mag you have to modify the MGC mag a little.
So far this fires and loads consistently well and as soon as I feel the urge to clean loads of cartridges I`ll get a video done .
Oh and you have to file down the outer dia of the head a little or it will get stuck in the chamber .
Certainly gives the gun a better kick
DOC