I'm not an expert by any means I just know what I have. I would assume since it is a .223 bolt face it's probably a small shank but that maybe a dumb assumption. Any way you could measure the diameter where the barrel screws in?
you have a small shank barrel. youll need a new barrel, new bolt head and a headspace gauge. and may i suggest, if you haven't already, replace the original recoil lug with an aftermarket precession ground recoil lug from midwayusa.com. i did this after the fact and i shrank my groups buy 1/8". not bad for a 35$ investment. im currently getting 1" 100 yard 10 shot groups with load development 308 loads. Good luck!