Yeah, this is a weapon file, not a map file.
Some private servers have encrypted their model data differently in order to prevent people stealing models.
This appears to be the case here.
Easiest thing to do in a case such as this is rip the 3d model directly from game memory.
You can use
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Go in game, find a player with the weapon model you want, then export entire scene.
Find the weapon you want in the exported 3d world model and go from there.
That's how I went about extracting 3d models of weapons from Guild Wars 2 for a friend who wanted their weapons in PT.
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