Use a small amount of break-free just around the head, ( because paint and corrosion can bond the heads to the retainer bars) then use a square tipped gunsmith's screwdriver tip, not a standard tapered one. It must fit squarely and exactly.
Laying the rifle on a towel flat on the table,give the screws a very slight bit of pressure
clockwise, then with
full downward pressure turn them counterclockwise to remove them. If the screwdriver isn't the right fit you'll ruin the heads. If that happens contact Guisan here.....
http://theswissriflesdotcommessagebo...MINISHOPS.html
He'll send you replacement screws. Its not hard to doi but you have to take your time and definitley use the right driver.
Latigo