Since the .300WM headspaces on the belt, how exactly does the headspace get to be excessive?
On the .300 WM barrel I had TC had reamed the chamber too deeply leading to excessive headspace. Also, with the large case head/high pressure rounds, the encore action actually will flex slightly (opening at the top of the action) which can exacerbate existing headspace issues. Various TC sites will talk about shimming the Encore action to help mitigate the headspace issues, but none of those things address a grossly overpressure round that somehow mysteriously vanished. Almost sounds like some of the tests done in bolt guns with bullseye where the brass "vanished" due to the insane overpressure they generated even if the action held together...(Accuratereloading has the pics for this if I remember correctly.)
For the OP, I think you need to rephrase your title as "TC stock broke when I loaded up a grenade"-whether TC should have made the stock stronger I'm not sure, but I shoot a .458 Lott and .416 Remington on my plastic stock Encore with no issues... I fail to see how based on the evidence you've presented the action actually failed as even on mine when the case ruptured the case head and body were still in the gun...
