Just so I don't get missunderstood sometime in the future. --- If accuracy falls off after shooting jacketed extensively, jacketed fouling buildup is almost certainly the problem, and the fouling must be removed. LBT push through slugs are the best way to monitor the amount of fouling, by simply running one through the barrel and measuring. If diameter has closed up till it's close to the point where accuracy fell of previously, clean the bore before you print some bad targets, or miss a nice game animal, (or bad varmint).
Also, each gun is an individual. I have some that will print the first shot perfectly when switching between jacketed and cast. Others will print the first one a bit off, then settle in.