I can see how this case might not really have been about pressure too much at all though and not argued too hard by either side.
The allegation was that the firearm opened up upon firing. I imagine, TC argued that it didn't open at all. Without an obviously grenaded gun, both sides probably wanted to steer clear of the pressure issue, considering it not entirely germane to what happened and with the potential of opening paths that neither one wanted to go down.
In fact, that is probably how TC got the expert testimony on the pressure of the loads excluded. They probably argued that it wasn't an issue as that they hadn't alleged that they loads were over pressure.
