  High-energy collisions can occur for radially moving charged test particles
in the extremal Reissner-Nordstr\"om spacetime if one of the particles is
fine-tuned and the collision point is taken close to the horizon. This is an
analogy of the Banados-Silk-West (BSW) effect, first described for extremal
Kerr black holes. However, it differs significantly in terms of energy
extraction: unlike for the original BSW process, no unconditional upper bounds
on mass and energy of an escaping test particle produced in the collision were
found for the charged version. We show that these results can be replicated for
the motion of charged test particles along the axis of a general extremal
rotating electrovacuum black hole, also including the Schnittman-type process
with reflected fine-tuned particles. This brings the possibility of high-energy
extraction closer to astrophysical black holes, which can be fast spinning and
have a small "Wald charge" due to interaction with external magnetic fields.
Nevertheless, we find numerous caveats that can make the energy extraction
unfeasible despite the lack of unconditional kinematic bounds.
