I've got a Savage 24, .222 over 20 ga. mag with El Cheapo 3-9. Give me about 2 weeks and I'll maybe have a more definitive answer.
A couple or four hunter ed. students over the years have told me they've centerpunched 'em with .223 55 grain soft points without much meat damage ...
My brother though sez rifles for turkey is " cheatin' ". He borrowed my combo gun a few years back. Knocked a gobbler off his feet with the 20 gauge barrel. And it promptly got up and flew off. Guess who went back to a 12 gauge. ?
FWIW, the barrels on the Savage combo guns are not necessarily "in tune", so allow yourself some time to put some lead on paper in advance. When my scope is zeroed dead nuts with the rifle barrel, the best part of the (full choke) pattern with the shotgun is low and left ...