Many folks have noticed that a factory clean barrell creates larger groups until copper fouled a bit, and then groups tighten up.
I clean with Hoppes, Kroil and occasionally CR-10 if I think it's getting overly copper fouled. Just to get the dirt out, not a deep clean, unless I know the rifle is going to be put up for a while. If I'm putting the rifle up for a long period I will gently deep clean which includes removing the copper, lead fouling and so forth. Be gentle when cleaning also, most damage to the bore is done by trying to clean improperly, without the use of a bore guide and getting too aggressive. YMMV, especially for custom barrels like Shilen etc, but usually a little fouling will help keep the groups a little tighter.
Another tip, DO not use CR-10 or any other agressive copper remover (Read: Ammonia based product) followed up by Shooter's choice, it will etch your barrell chemically i.e. hose it up big time. Use rubbing alcohol or some brake cleaner or a patch to degrease and deactivate the chemicals in the cleaner followed up by a light patch of oil, or boresnake treated oil. Those boresnakes are great tools, but remember to clean them in the washing machine regularly, why introduce more grit and dirt into your chamber/bore.
Don't overlook, or believe all of the hype about Copper Fouling as being horribly bad for groups by solely focusing on it. Get a good powder solvent like the trusty old Hoppes #9, most accuracy decreases due to a build up of powder residue (crust, if not addresse) just ahead of the chamber. Get a good chamber brush for your caliber and clean it gently but thoroughly and degrease.
CLP works fine for daily maintenance. But my opinion, (MINE) is that CLP does none of these functions really well (Clean, Lubricate, Protect) for long periods of storage or normal civilian usage or maintenance. Like stated by others the military is diligent in daily or multiple daily cleanings if warranted and in that case it works pretty darn well.