tp,
It will have more to do with the ambient temperature at your location, than anything else. If your temps are running in the 50 degree range your cool down time will be a lot less than if it is 100 degrees like it is here. Generally in cooler weather, by the time you clean out between shots (unless you are a speed cleaner) the barrel will be cooled enough to give you an accurate assessment of your loads. If you are in hotter weather you may want to let your barrel cool a little longer, or use something like cold water to clean your barrel between shots.
Real accuracy between shots will only be true over a clean barrel, so take your time at the range, and plan to spend all day to get a good accurate load worked up. When ML hunting, the only shot that counts is the first shot, so you want to duplicate your hunting conditions as much as possible. For most of us that means one shot from a clean barrel.
If you are in high temperatures you might want to keep your sabots in a small Ice chest, and a dry freezer pack, and keep them out of the sun. They will get soft in the heat and will do more to throw a shot off than if they are good and cool. Sabots will also get soft if they are run down a hot barrel. I don't use conicals or patched balls, so I can't comment much on what heat does to them, but heat will make a big difference in a saboted round.
More of a direct answer to your question would be in cooler weather, around 2 to 3 minutes for cool down and in warmer weather probably 10 to 15 minutes between rounds. Main thing in any weather, is not to get in a hurry. Working up a good accurate load is not a speedy process, and the more time you spend doing it right, the better your results will be.
Hope this helps.
