The general concensus appears to be that most rofles shoot better from a fouled bore. I always clean my rifles after a day at the range or hunting.
Why is it necessary to remove every last trace of copper fouling from the barrel? Would it be detrimental in any way to the barrel to just remove lead and powder fouling and not worry about the copper.
To be honest, I use Sweets maybe twice a year when the rifles get a thorough going over and my rifles all shoot tight groups.

If one is going to fire more than one shot without cleaning then those groups, by definition, are fired with a fouled bore.

A lot depends upon how smooth a bore is and how hot the load and numerous other factors just one of which is the type and quality of the jacket material.

I have a pre64 M70 in .300 H&H that I shot today. It's bore has obvious tool marks in it but this rifle shoots so well as long as the bore does not get loaded up. I think it's maximum is around 15 to 20 shots. Even after Hoppes 9 is run thru the bore and then a brush you can hear the noise from the brush scrapping metal fouling out and I can see a spray of fouling come out when the brush leaves the bore! Today with it's full power load of 165 Sierra SBT's it shot a 5/8" group with the last two going in one hole. I moved the scope down 1/2 minute and two more shots when right together 1/2" lower at 100 yards. I will not clean this rifle as it's ready!

Other rifles with really smooth bores will shoot at least 150 shots without cleaning. Some that are having problems I clean a lot more out of frustration than anything.

Once a rifle shoots a load well it's best to save a few shots, put tape over the muzzle and go hunting.

I'm beginning to slack off on my cleaning a little. I will go after the copper when I look down the barrel and every land is covered with a solid streak. Otherwise I think a little kroil in the barrel and back to the gunsafe. I'm also beginning to like taking a boresnake to the range and run it down the barrel every 10 shots or so. (or when trying a new variety of bullet etc). I still like wipeout. It may not get the barrel spotless but it sure is ez to use. I dry patch it and go after the copper with something else like butches, sweets, or rem borecleaner if need be. Seems like wipout gets at least 50% of the copper on the first treatment. I think I have too many darn cleaners but, the task is getting easier and easier with the new products.

Copper fouling will eventually build up to the point that accuracy suffers if you don't remove it. You probably don't need to clean your rifle after every hunt, but I always do. The phrase that more rifle barrels have been ruined from incorrect cleaning than from not being cleaned seems to be crap to me. If you just leave the copper fouling there, moisture, powder and other goodies can wedge between the barrel steel and copper fouling, and cause unseen rust. This is the key reason for getting rid of it. My motto is to keep my barrels like teeth - CLEAN and they will last forever. Some barrels seem to shoot OK with mild copper fouling, and others seems to deteriorate quickly. If you have a quality barrel, chances are it probably doesn't foul easily, in which case you won't need to worry about it too much.