Well target shooting, especially hard core blood shooters need to eliminate all variables as much as possible. They weigh ball down to a grain or two or even half. Weigh powder charges, near dry patches , every little trick they can think of and threat produces the smallest possible group
I shoot any ball that doesn’t have visable defects. Pour my charge in a rough measure. Shooting for sight in and just practice I’ve not noted difreabcs between first shot and tenth, but do swab my bore between shots, I don’t know how that effects what your looking for
But I would hazard just from basic physics a fouled barrel that is cold, as in a hunting day near freezing is going to shoot different then a warm, from both the ambient temp and the warmth of ‘rapid’ shooting, barrel sighted in during 70 degree plus weather