1919a4 parts kit - breech block cam lock screw removal

[Circuits]

So I've got this parts kit I'm getting ready to build. The breech block cam lock screw is staked on 25 ways to Wednesday. I've used my biggest screwdriver, body leverage and a crescent wrench on the blade flat to no avail. Any suggestions for getting the sucker out so I can rivet and finish the bottom plate?

Am I doomed to grind or drill this sucker out and replace it?