9mm +p+ and major

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Not hunting reloading I know but thought the wealth of knowledge here could get me to the right place. I read a lot of people specifically avoiding loading +p+ ammo reloading but once I learned of 9mm major I found a lot of people really pushing limits with the 9mm even further. I may be completely misunderstanding but it seems that “major” is ++p++. It appears that these loads require compensators and well built (likely custom) firearms so this is really an academic at this point. Does anyone have good resources for load development? Firearm selection? Maybe some books or websites? Preliminary research says this is word of mouth and witchcraft. Thanks.