Ever since i was a lad, I have been obsessed with James Bond. In From Russia with Love, there is a scene with James Bond and Karim Bey taking out one of the villains.
The whole scene is here https://www.youtube.com/watch?v=iSUR050VECM
Bond whips out the AR 7 and assembles it, from a custom stock.
I am lucky enough to live in a country where I can get hold of an AR 7, as used in the film.
Here is my take on that.
Lot of geometry involved to get the receiver and the barrel at a certain angle within the stock to keep to the dimensions of the plastic stock it comes with.