Startup initialization phase of the Heretic powered Phoenix Rod attack.
Fire: PHNX B 3 A_InitPhoenixPL2 Hold: PHNX C 1 bright A_FirePhoenixPL2 PHNX B 4 A_ReFire Powerdown: PHNX B 4 A_SubtractAmmo goto Ready
Only callable from a player weapon state (or, unusually, from a player avatar actor). Sets weapon counter 0 value to 350 (which in Heretic means 10 seconds of firing).
You can just use WeaponSetCtr to achieve the same effect.