I am familiar with full blown leading when a misfit bullet or trying for too high velocity lets gas past the bullet and plates the bore with lead that is no fun to remove. My experience is that this ruins accuracy immediately and wild shots get wilder if you keep on shooting.
I have been seeing another type of lead in the bore. With some loads I can feel resistance to the first patch part way down the barrel and long slivers of lead come out on the patch, sometime even thin foils of lead. A second patch will usually go through the bore smoothly so the lead seems to usually comes out easily as opposed to the results of real leading.
The strange thing is that the rifle will usually continue to shoot fairly well (not its very best) in my recent shooting the rifle was a 223 shooting an 85 gr bullet over light charges of fast burning powder at between 1,300 and 1,500 fps. The rifle usually averages 5 shot groups of around 1 MOA even when these slivers are coming out on the patch afterwards.
The bullet seems to seal into the throat and even passes the Bill Caffee baloon test so it is hard to see how gas leakage is the cause and if it is why does the lead come out so easily and accuracy stay reasonable good?
Has anybody had this happen? What is the mechanism causing it? What is the cure?
John