I try to use traditional methods and materials for repairs whenever I can.

The original material used for the repair was one wrap of brown paper around the tenon, stuck on with shellac and one coat of shellac on the outside to seal against moisture. I have a template for the paper shim. Usually one wrap will do it, sometimes two.

The butt socket has a taper so that the further the butt is drawn into the socket, the tighter it gets. Sometimes a good whack with a mallet it needed to get the butt to seat. Don't beat on the butt plate, it will distort. Use a wooden dowel (eg. a section of a broom stick) inserted into the bolt hole (bolt removed) to drive the thing forward.
When tight, there should be a small gap between the shoulder on the tenon and the back edge of the butt socket. If the shoulder touches, there is a risk of wood chip out along the grain under recoil.

Modern materials are great in certain applications. Assembling the butt with a coating of epoxy on the tenon is a make shift repair at best, and would not allow the butt to draw up tight in the way that it needs.

If I found a vintage rifle with epoxy on the butt tenon, I would have to guess that it had been repaired in the home workshop by an owner in recent times.
If I found a vintage rifle with shellac and brown paper on the butt tenon, I would not know if it had been repaired by a gunsmith in 1918 or a hobbyist in 2018.