If I swap out for a new competition barrel, would I have to go through boxes of ammo until I find the one it likes, or would it just naturally break in and like the ammo I start it off with?
You'll have to jump through the hoops to find which ammo the barrel likes best...but you'll also find that your barrel "likes" a larger assortment of decent ammo. Wolf is great, Fed. 510 is very nice in my barrel, and Fed. 714 is crazy good (it will show my trigger/aiming mistakes)