A Western Field .222 is most likely a brand named Savage 340.
Before I got into chamber reaming, I would see if the magazine would hold and feed .223.
I would also consider the rifling twist. It most likely has a 14 twist for 50-55 grain flatbases. M193 55 gr boattails might work, the Army did not change the twist from 14 to 12 until they did cold weather testing.
The 45 gr WWB would be fine.
But 62 gr M855 would not.