Sojourn's Railgun

If Sojourn, Expert Marksman is your
commander or is in your deck, start the game
with Sojourn's Railgun on the battlefield.
If Sojourn would deal combat damage, put that
many charge counters on Sojourn's Railgun.
{1}, Remove X charge counters from Sojourn's
Railgun: Deal X damage to any target, where X
is the amount of charge counters removed using
this ability. Sojourn's Railgun can only have up
to ten charge counters on it at a time.