I have a 6.5 Grendel AR that I love. I would also like to do a build for a bolt gun. I think you would be fine with the .223 mag. My AR platform will run fine out of standard .223 pmags. The 10 rounders feed fine and so do the 30 rounders. It when you get down to the curved part of the 30 round mags that you run into a problem. I think you will also have to change the bolt head, as the diameter is different. Keep us posted on your project.