Hard FPS drops only in First Person Shooters? Need some Tech advice!

Pretty much exactly the title. This isn't happening in 3rd person games, but in FPS such as Halo MCC or CS GO, my frames will drop dramatically from time to time exactly when I do something like fire a shot, such as from a sniper or the Deagle. Has anyone had this happen?

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Specs -

Ryzen 7 2700x

MSI RTX 2080 Gaming Trio

32 GB RAM

1tb SSD

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Note - I am running these games off of an external Hard Drive, could that have something to do with it? It's a USB 3.0 Connection? Just a thought. Any help is welcome and feel free to call me a noob and point out the problem I would just like some help fixing it.