Topshot, you are correct. My gunsmith confirmed today that the Howa actions are cast. That being said, So are (or were) the Mark V actions used for the big Weatherby cartridges, and in his opinion they are strong as a Rem action. He has built multiple hundreds of Rifles on the Mark V and estimates about 100 on the Howa in just about every cartridge. He has a very favorable view of them and has no problem with building a Lapua cartridge on one. So, I'm fine with my decison to do a 375 Ruger wildcat on one.
A couple of questions comes to mind when looking at that photo. What caused that failure? Too hot a load perhaps? And what would have happened to a Rem action without the gas ports in the bolt, or the one piece bolt construction? Stupid is as stupid does and I've worn that hat a time or two, but fortunately haven't blown up a rifle yet.
I am glad you brough the subject up as it has been a learning experience.