How do you get the scottish resistance on team fortress 2

You unlock it the same way you unlock all of the other weapons. Over time when you get achievements and kills the kind of just appear randomly. Like I just left my game on for about an hour and a half to go eat at macdonlalds and I came back and on the screen it said that I had unlocked the force of nature. And at one point it had been 2 months and I had only unlocked 1 weapon. But you can unlock the same weapon multiple times. Like at the moment I have 3 direct hits. And it took me about 3 months after I bought the game to unlock the sandvich. But for my friend it was the first thing we unlocked.