Said that, does anybody know if it's possible to get a Winchester 70 action only?
You might be able to pick one up on Gunbroker, but nobody I know of sells only the M70 action for building rifles. The closest one would be Montana Rifle Company, they make a close clone of the M70 Winchester. If you want an affordable M70 action try to find an old push feed M70 one of the most underrated actions IMO.
Bart B.
I never said that Ruger had a stronger frame I just simply said they were larger (beefiest using OP term) because they were investment cast. I have know way of testing the strength or flexing of the action nor do I care. The Ruger receiver is just cast to save manufacturing costs, and they make darn good hunting rifles IMO but I'd never choose one for a target rifle.
As to the Remington extractor I'm no expert on them either I'm just going off what I've read or been told. I've had a M700 for nearly 20 years off and on and none have ever had the bolt handle fall off nor the extractor break over 100's of rounds. I don't shoot 1000's of rounds through them as they have all been hunting rifles .30-06, .270 Win and most recently .35 Whelen. I'm just going off what I've read on extractor failures and what Rich Riley told me from High Tech Custom rifles. He makes a living building M700 rifles as his main bread and butter, he does several Sako mods a year but told me I didn't need to fix it until it breaks.
Having the extractor snap over the rim might weaken them like you say, but an overpressure round that is hard to extract will put a lot of force on the extractor as well. I imagine a few hot loads are going to put more forces on the extractor when "extracting" than one "blue pill" at the factory or several hundred rounds being cycled through the rifle. Of course this is JMO with no scientific evidence to back up the claim.
All machines have a certain amount of wear and the M700 is no different, parts that wear will eventually fail. Ufortunately we can't predict when the failure is going to happen so you have two choices be proactive or reactive and I'll be the latter when it comes to the M700 extractor.