I agree whole heartedly, that if shooting without wiping, that over the course of the day, the rod does 'climb' with the buildup of fouling in the breech area.
With no wiping, the fouling that does coat that powder-chamber-area of the breech does build up over a number of shots - as in about 1/4" over 30 shots
or so, depending on the calibre and amount of powder used.
The fouling does not build up because of the previous shot's fouling being pushed down as it is loaded, though. To state that, I think is incorrect, I think. That
previous shot's fouling is shot out with the patched ball. There is no ring of fouling in my bores after shooting the trail, whether 20 shots, 40 or 90 (long day of shooting).
Oft times, I will drop a squib load down after a long string of shots, say 20gr. in my .69 or 10 to 15gr. in the .50. When I load that patched ball, there is no fouling ring
to have to push past . That ball loads almost normally, right down on top of the powder. There is extra fouling there in the powder chamber area, but not a ring of it. If
there was, it would be felt. The reason for shooting that squib load, is to remove most of the fouling from the breech area, thus there is only a small amount there, plus
what is left in the bore from that 'squib' shot. It's also fun to shoot at the 25yard gong at the start of the trail and hear a low, soft "pop or pow-----------tink".(clank with
the .69's 480gr. ball)