For loading .224 Valkyrie in a bolt gun, a neck size bushing of .253 is a good starting point, especially if you're using standard brass. This size should give you a nice fit while allowing for good neck tension on the bullet. However, it's always a good idea to check your chamber dimensions and possibly try a few different bushings to see what works best for your specific setup. Consistency is key, so once you find the right bushing, stick with it for your loads!