This is *especially* easy to see in an inline muzzleloader with a breech plug. Just this past weekend, I was shooting and running a bore snake down the barrel after each shot. Just as you describe, most of the barrel would come out shiny clean except for that carbon ring right down by the breech That took some solvent to clean out.It's taken 30 yrs to learn that?
The last 22" of a 24" barrel cleans up fairly easily (from the chamber end). The first 2" is a different story. I will bet money, the vast majority that think their barrel is prefectly clean, have a huge carbon ring at the throat.
BearTracker, I'm willing to bet 90% of the hunting rifles out there, that guys have just spent 20 minutes cleaning, still have that ring of carbon buildup, but when it comes to loss of accuracy, how much difference are you proposing that it makes? To be frank, the vast majority of TRULY clean rifles will require a fouling shot, or three, before they can shoot their best groups. Could it be that this is needed to reapply that thin carbon layer at the throat, thus smoothing the bullet's entry into the lands and actually improving the accuracy of subsequent shots? That could just be crazy-talk, but if carbon buildup is a culprit in reducing rifle accuracy, wouldn't groups start to get worse after the first few shots, instead of getting better and better...before finally starting to open up? Surely carbon buildup doesn't increase greatly after the first few shots, as it will only persist where the friction from the next bullet doesn't scrub it away?
The keys to accuracy begin with concentricity where the bullet is introduced to the bore (case neck, throat, etc.), is enhanced by consistent and precise loading techniques, and is finally determined by the opposite end from which your concerns arise; at the crown of the barrel. If I had to allocate percentages to which of these things affect accuracy, during the course of a full range session (say 60 rounds), I don't think carbon buildup at the throat or leade would garner even 1% of my vote.
By the way, carbon, in graphite form, is an exceptional and durable lubricant. A heckuvalot slicker than a grooved steel barrel, anyway.