JD,
I will do some hunting on the SAAMI spec on the 9.3x62 and see if I can find it. It shouldn't be high pressure cause of the big bore. Your K-98 was heat treated better, so was my G33/40.
I am am not trying to scare anyone on not using a 09 action, there good sevicable actions, just spend the few dollars and heat treat them and then you have nothing to worry about. I have a small ring Mexican mauser that if I use iit I probably go the same route. And once the 09 action's are heat treated they are strong, the weakness wasn't for lack of metal in the design, or poor design, it was heat treating methods when they were manufactured. As a big blanket statement I am suspect of anything made before WWI, and by the mid-late 30's manufacturers were doing a much better job in this regard. The big advances in heat treating happened right before and during WWII and post war guns are much better and were using modern methods. And no I'm not saying that someones pre war model 70 is and issue, cause that isn't true, both Winchester and Remington had this worked out way before that.
I soul searched this weekend and decided I am not retiring my G33/40 7mm. It just wasn't going to happen for less than $3000-4000 and a custom rifle, I like the rifle too much. I made a command decision I am going to build up another rifle and see where it goes from there. My thoughts on this are; a Model 700, with a three position safety, change out the bottom metal to steel. Krieger barrel, which I am going to get long and figure out how short I can cut it later. I have a good wood stock blank for this, so a stock and checkering project is in store. I am also thinking of getting a McMilian stock so I can swap it around. I am going to chamber it in a 284 Win.
One last comment on building on the old Argentine actions, the one big downside is value after you get them built. Depending on how much work you are plannning on a custom they can be a black hole for dollars which you can't ever get back out if you sell it. If you do the work yourself and have the tooling this can be a labor of love so to speak, and helps. But the reality is your better off starting with a slightly more expensive action to start with. Do the math, if you start with the 09 and pay $150-200 for the action, then add changing the bolt handle, some mill work cleaning it up, heat treating, changing the safety, buffing and polishing you have over $400 into it easy. By the same token if you started with a Sako or even a Remington you paid that up front for the action but when its done its worth about about twice that the mauser is. Not all mausers are that bad, and there are some models that are worth the effort, but look on gunbroker or gunsamerica and see how many "custom" mausers there are at not much over $500. Enfield customs suffer the same problem.
I don't sell many guns so I build or buy what I like, but I do try to be smart on this and don't like dumping dollars into projects that there is no upside to if I ever decide to sell it. A for instance is if you built the same rifle on a Pre 64 Model 70 Winchester, yeah initially you will have $200-300 more into the action. But you have no changing safeties or bolt handles, no additional work, so you save that cost, which gets this close in costs. But when its done the Model 70 is going to be worth way over a grand. And in the 9.3 bore that would be a very sweet rifle.
From my digging around research on my own projects, and based on what I found if I was going for a 9.3 caliber rifle, go look at SARCO. They have some 9.3x57 Husky rifles right now. They can be had for $250-300. The bolt handles are bent, they are a good strong action, and all that needs to be done is run a reamer through the barrel, set it back a thread and your done. I think this could be a done deal for under $400, I just don't see a cheaper route and you can always get your dollars back out if you decide to.