Here is was I would like to do I have a 12BVSS in 223 and I have a new McGowan barrel in 220 swift that was for another build but the stock in running late. So my question is I know I can put the swift barrel on the 12BVSS but I need to change the bolt head. What is the difference between the 110 series bolt head and the 12 bolt head? By looking at the descriptions in midway the two bolt head are not interchangeable.