Barrel nut is the same.

Bolt head, barrel, and magazine are different.

You can do this yourself with a 223 barrel, .378 bolt head, 223 magazine, barrel nut wrench, dead blow hammer, sturdy shop vise, notched hardwood blocks, brown sugar, appropriate GO GAUGE and Scotch brand clear tape. Might wanna spring for a new ground recoil lug at that point, too.

There are videos on Youtube that show you how easy it is, and after you do it the first time, should take you 15 minutes TOPS to do it thereafter.

Jim Briggs at NSS can fix you up with everything you need, but you can get barrels from a number of different places and gun parts (bolt head, magazine, etc) from places like Midway & Brownells.