Even though my MES has a max of 270 when smoking outdoors in the summer it will go up as high as 285 according to my Mav thermometer. I always run it at max when doing turkey or chicken and although I wouldn't call the skin crispy it is at least bite through and not leathery. It would be nice to get to baking temps.
Mine went up to 295º last summer but it wasn't intentional; I had neglected to clean the hi temp limit switch so the temp kept increasing. I cleaned it and temps were back to normal. A couple of guys reported their MES 30 or 40 Gen 1 got up to 325º or so also unintentionally. My point is that the MES is capable of higher temps than 275 but the overheating could cause permanent damage to the smoker so it's not advisable to try for it.