Good info! I use CCI mag primers in my 9mm loads and 45acp. Well, I use standard and magnum. I haven’t really noticed a difference. I’d assume powder would be a factor as well. Oddly, I haven’t chrono’d Standard vs magnum. I’m running well over base but under max, titegroup.Magnum primer in general are used with specific cartridges or with powders that are not easily ignited due to powder density such as ball powders. Anytime you change a component such as a primer type not listed with the load data one should always work up the load from scratch. Not all magnum primer are alike some are hotter than others and can cause pressure increases and with the 9 mm being one of the most sensitive to pressure issues I would definitely start at the minimum load data an work up slowly.
There are instances where the use of a magnum primer in small cases can start the bullet to moving forward before the powder has a chance to fully ignite which can cause some erratic velocity, ES and SD reading on the chrono.