I need help (again) with my story, how much historical detail should I put inside my fanfic? For events, it's a must. It's unavoidable. But what about weapons and vehicles? I want my fanfic to be readable by both history buffs like us and some people who don't know much about history like us.

I don't want to make into a gun/vehicle porn. Should I not throw details on weapons and stuff? I mean, I can say that this pony is wielding an MP40 but I feel like there's no need to specify it. I also don't want to exhaust myself doing a lot of research.

Well it depends on how much you want. If you want a lot of detail but not overwhelm the reader go for a good mix of historical detail and non historical detail.

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For me, whenever I do a fic that is historical base in any sorts, it falls into the same category as world building. I have the same approach in which even you might have to ask yourself the following question. “Which is more interesting: an encyclopedia that’s filled with facts, histories, and origin of everything about a particular world in excruciating detail; or having a character describing that world from their point of view?” I tend to go to the latter because while describing something historic can be necessary for the environment, culture, and viewpoint that character has not only lived in, but from the character that experiences it too. Because if you write it that way, we the readers would experience the same thing as well.

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What Inkwell said.

That, and do the readers need to know/would the main character/narrator feel the need to let them know? It might be important that whoever's shooting at them as an MG 42 so that it gets a mention boy name?

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At the risk of being a bitch, I think I got it right with my old A Great Endeavor. Short, readable descriptions of events so those unfamiliar can grasp the context. Less technobabble is better, but it should be clarified or implied what everything is - a Thompson is a sub machine gun, a Tiger is a heavy tank, etc. Nothing is going to break immersion like clarifying exactly which Pz IV variant is on the scene and how it differs from its fellows. It's even okay to say "The German tank" instead of specifics if the POV character doesn't have much clue themselves.

WWII is the setting. The setting must serve the story, and nothing else.