Magnum P300 Maintenance Manual - page 3
To remove rear baffle:
Lift the bottom edge of the rear baffle to clear the lugs cast into the base of the firebox,
and then rotate the bottom edge forward and lift the baffle out through the firebox door.
To remove the air tube:
The air tube is held in place by passing through holes in either side of the firebox.
It is necessary to firstly remove the screw at the left end of the air tube, that holds the
tube's flange against the left side wall. Then, slide the airtube to the right until the left
end can be rotated down into the firebox to allow the right end to come free.
Take the airtube out through the door.
(Note that after extensive use, it may be that the screw is unable to be unscrewed. In this
case it will be necessary to cut the head off the screw with a grinder.)