Fixed. It's almost impossible to see the extra bit of barrel but I ended up shaving a few triangles off so I'll leave it be for now.
And when I said the site should "actually work like it does in the real world", I was refering to the fact that I'm putting it into a game/mod that should make use of that part of the model. EG. Working iron sights. Assuming I dont go and put a scope on it anyway.
Unwrapping it now.
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