Is there a period or comma in the 339 as 33,9 for instance. Can't remember the metric designation exactly but 5.6 x 33.9 sounds very close to the old German Vierling round which was a sort of go between from the older .22 WCF to the later .22 Hornet. This was I believe a rather common round in Germany & chambered in many guns other than Vierlings.

Old Farmer;
What makes it Illegal?? What am I missing here, whats illegal about a bolt action sporting rifle?

Miller/TN
I Didn't Say Everything I Said, Yogi Berra