5/8-24 so yeah I’d have to decide on qd or bushings to convert to 1/2x28 if I went direct thread.If you get one for your Creedmore, it will work perfectly fine on a 223. A 30 cal can will handle all three. You would need to pick a can that has interchangeable barrel mounts or one that uses a quick mount adapter and outfit each rifle with one with the proper thread pattern. I don't know what the thread pattern is for a 6.5.