In the summer when it is real hot I have noted a decrease in accuracy even if I swab between each shot if the barrel gets hot. You can tell if the barrel is hot by touching it. I combated that by shooting two different rifles, putting the shot one in the shade and letting it cool off after swabbing the fowling while loading and shooting the other one.

Others take a cooler with them and towels. After they shoot they swab then wrap the barrel in cold towels. I am sure that would help cool the barrel faster but I guess I would not go to that much trouble. Take your time swabbing, and check your target (if possible) and then take your time loading. Shoot in the shade if you can, it really does help.

Also conicals and round ball do not seem to be as bothered by a heated barrel as sabots. I think it has to do with the plastic getting soft.