Winchester brought out the Model 59 shotgun in 1959. It had a fiberglass wrapped barrel. I am not too sure how it relates to this subject but I'm pretty sure a jam-o-matic can get hot!
Yes, with a steel liner taking the brunt of hot powder gasses, pressure, friction, etc. There are also rifles using a similar system with a rifled liner wrapped in carbon fiber and high temp resin. This is like the difference between using epoxy to patch an engine block because the water jacket leaked, and trying to use the same product to line a scored cylinder.
KY Jon asks what you have to lose??? If the veneer of epoxy pops loose and creates an obstruction in a barrel already somewhat compromised by pitting, you could lose digits or an eye. A lot of dangerous experimentation has taught us about things like the strength of Damascus barrels. But when the risk became greater, the firing was done with a string pulling the trigger, and the shooter shielded behind a protective barrier or a big tree.
I think that the eventual failure probably won't result in a barrel burst, but the possibility certainly is there. Most likely though, you would simply learn that an epoxy interior surface is simply not up to the task, and it will never be a satisfactory replacement for sound steel in this particular application.
