sixfive,

I read on another forum the following, if it helps:

The krags were developed at a time where the metric (SI) was not yet used commonly (Still not ;-)). The screws are in the BSW *(British Standard Whitworth)
Size on the receiver is a mix of nominal metric and inch measures.

and:

Looked at some action screws (Norwegian Krag) I have. They seem to be 1/4 X 20 tpi.