not a lot to do with this marker. check eBay for some parts.
the F4 has the same barrel threads as the Tippmann A5/X7/Prolite/Carbine
Common upgrades include
- double trigger frame
- high volume cell
- venturi bolt with adjustable re-cock
Alamo city paintball makes a couple of delrin bolts for the F4.
A gas-thru foregrip can be added if yours does have one. Something I've learned is that the F4 needs high pressure and high airflow, so theres no point in using an inline regulator. You may be better off just running CO2.
Everybody: Let's ease up on the red loctite, 'kay? Thanks.