Investment casting has improved leaps and bounds since the 70's. Ruger has led the way in a lot of it. They investment cast most everything. Including their frames for the Super Redhawk, which comes in .454 Casull. Their bolt action Model 77, as well as the falling block action for their #1 rifle are all investment cast. Both are 2 of the strongest actions on the market.
But you guys are right about rechambering the older model Contenders, to calibers the Encore Pro Hunter comes chambered for right from the factory. 2 different animals. The IHMSA was instrumental in getting these beefier models of the Contender built. Those guys pushed the limit with everything back in the 70's, when that sport was starting out. Several of the early guns had their frames stretched, or were outright blown up because of rechambering to rounds that were never designed around the early Contender frame.
I remember back in the late 70's when Thompson released the Super 14 Contender in .30-30. I knew a guy who had one of the first one's. That kind of power in a handgun was unheard of back then, from a factory chambered pistol. It wasn't long after that Remington came out with different versions of the XP-100 in bigger calibers, and it was game on in the single shot handgun world. Today the Encore Pro Hunter comes right from the box chambered in both .308 and .30-06. And from what I've been reading they hold up unbelievably well. I can't wait to get mine out and crank it up!