I have lefty friends too and I feel for them when they try to find firearms that work for them. +
As someone else mentioned, with the right twist rate the
223 can use bullets up to 90 gr accurately so with proper bullet type and appropriate range, it is certainly as capable as the 30 30, can equal the
243 bullet size with only slightly less velocity so at the shorter ranges don't see why it would be problem. As always shot placement is the key.