MCB, let me be the first to welcome you to the Nitro Express forums! You will find a lot of first hand experience here. That is not to mean these folks will always agree on the answers to questions like the one you pose here! You will get everyone's favorite round, louded as the magic one that nobody can live without, but there is where your job begins, sifting through the info you get, and selecting something that works for YOU!

My answer to your question is as follows. Your fondness for the pre-64 mod 70 is a good place to start, and is a very good choice as a platform for your DGR (Dangerous game rifle). But, IMO, the first mistake you are makeing is looking to the 458 Win Mag in that mod 70. A far better value would be the 375 H&H, of the rounds avaliable in that pre-64 mod 70. Unless you hand load, the 458 Win Mag has some serious draw backs in it's design, and the 458 LOTT, is what the 458 Win Mag should have been to start with. The 458 WM doesn't have enough powder capacity to handle 500 gr bullets properly, and that fact rules out factory ammo, for hunting dangerous game. Even with careful handloading, and bullets no heavier than 480 grs, and 450 grs would be better, the cartridge is still not up to the job that can better be handled by the LOTT, or even one of the 416s. The first thing you need to know is that if you get seriously into big bore shooting, you will have to handload, in self defense, because factory ammo for any of the REAL BIG BORES, is very expensive, and if you ever want to get that double rifle, you better set up to load your own!

A pair of pre-64 Mod 70s one chambered for 300H&H, and the other chambered for the best all round cartridge in the world, the 375 H&H, and you have a classic pair of Safari rifles of the first order, both collector items as well! The 416s are fast comming up on the old 375 H&H, in popularity, and they are good ones. What you don't want to get into is the ULTRAs, by any of the makers, they won't do anything better than the origenals, but burn more powder, and make more noise, and recoil, for no gain in effectiveness!

But if you want something NEW, the Ruger you mentioned, now chambered for 416 Rem Mag,or Rigby and the 458 LOTT would be a great choice, but untill I got a little experience with big bore rifles, I'd stick with the 375 H&H, and another choice is out there as well. The CZ 550 safari is available in 375H&H, 416 Rigby, and 458 WM, which can be re-chambered to 458LOTT, and it IS true that the 458 WM cartridge can be safely fired in the lott chamber in a pinch, if your ammo is lost in transit to a hunt.

My personal favorite are the NE rounds in side by side double rifles, but you already said you can't go that way, right now. I completely understand, but that doesn't mean you can't join the big bore fun. Like I said, I'd start with a good 375 H&H, and hunt everything with it for a couple years. A CRF rifle chambered for 375 H&H can always be sold without looseing your shirt, to buy a 458 Lott later, if you decide you want something bigger. This is my own opinion, but I beg you not to fall into the 460 Weatherby following! Stick with the old classics, and you will do much better, in the long run!

Again welcome!