Are weapons one of our biggest exports?

No.

Well, not first glance.

Writing from the UK here, if you look at the latest government data they put the value of all our defence exports at £7.9 billion in 2020.

Now, £7.9 billion sounds like a lot, and it is. But compare it to our biggest exports. In the same year we exported £121 billion of business services and £64 billion of Financial Services. Alongside these the defence industry looks relatively small.