I've got a lefty RAR in 308. It's light, shoots great and I don't worry about it in weather. If I wanted a lefty 223, I wouldn't hesitate on a RAR. CZ made it's mini Mauser in 223 if you want walnut and blued steel and can find one. I think they were twisted rather slow which may be a concern if he intends to shoot heavier bullets.....

Bore size is no substitute for shot placement and
Power is no substitute for bullet performance. 458WIN