Very few mass produced rifles have had their barrels properly lapped, which means that the bore is as-machined. More often than not this means that bullets will slowly polish the surface and it usually takes a couple of hundred rounds before it's smooth enough for excessive copper fouling to stop.
Personally I prefer to hand-lap barrels, a routine I've had for some three decades, and when done properly the results vary from good to great. No fouling to speak of, muzzle velocity increase of 20...100fps depending on the rifle and quite a bit more consistency both in fps and accuracy. Casting a lead lap into a pre-heated barrel requires some care and gauging the barrel beforehand is a good idea, but the lapping process itself isn't that difficult and while ruining a barrel is possible, it takes quite a bit of effort. What you're aiming at is uniform resistance from the chamber to 3-4" from the muzzle and slightly tighter feeling muzzle end. I've also moly-coated some barrels after lapping but haven't found much meaningful difference.
So it's all up to you. Learning to lap a barrel is an experience but not absolutely necessary unless there are serious burrs or other irregularities that shouldn't be there in the first place. Bullets do (some of) the job for you after a while, too. Hand lapping has been mystified a lot lately but all in all it's a fairly simple job that can potentially improve the barrel quite a bit. Even a finished one, in spite of myths that only barrel blanks (hah) should/could be lapped properly.