i have a MS sporter that has recently begun to show a 100-300fps variation in factory ammo. the wide ES doesn't seem representative of what is happening down range. everything is still grouping sub moa out to past 700 yards. any other time i've had an issue with the magnetospeed it has been related to the bayonet moving or not being at the right gap from the travel of the projectile. i've ruled these out through careful observation in this instance. so that has me questioning if there is a recalibration procedure for these?