Great Googly Moogly!
I done went and fetched me up a
metallurgist! 
In the context of the fact that I am most certainly NOT a member of that august profession, nor am I any kind of chemist, I count myself lucky that any of the hard-delivered pronouncements I leveled in my initial post about stainless' properties haven't drawn any negative criticism!
My experience with the stuff dates back to the first job I got out of high-school, working in a dinky shop in Palo Alto making high-vaccuum manifolds for Hewlett-Packard mass spectrometers. I started as the shop-helper. We cranked out 13-20 of these things, with associated flanges to hold componentry, per month on old Monarch lathes dated 1942 on a U.S Navy ID plate.
These T-shaped things were cold-forged out of 1/8"-wall 4" dia. tubing, with flanges machined from forgings. They had to be precise beyond the bounds of reason, (.001" or less squaritude and concentricity over a span of 18" or so, with a 6" extension at a right-angle to the body.) but if you ran the machines right, they'd repeat reliably.
I got REALLY GOOD at building these things, as well as anything else we had going through the shop. I learned most of my "formal" machine shop training here, as I hadn't had anything other than high-school metal shop before. Within the space of six months at the job, I was making EVERYTHING. I was the lead guy, at $4/hour shop-help wage. (In '86, we couldn't get competent help. Everyone who was worth a darn HAD a good job.) Anyone know what an H-P spectrometer cost back in the late eighties? I'm curious, as I made 100% of their componentry for a space of about two and a half years. I imagine my manifolds and flanges are in test facilities all over the planet.
I wasn't even 18 yet. After I worked there a year or so, I quit to go back to school, which was my original intent, but proved to be a fruitless endeavor. I don't dig school environments much, and I got booted from the parent's pad. So I went back to the old boss, and asked if he needed help. He did, as he was a one-man operation, mostly, and he STILL couldn't get anybody who could meet H-P's anal quality levels without botching a lot of stuff on the way. I just picked up where I'd left off. I still had the friggin' numbers for the parts memorized.
I did get a 100% raise, though. Still cheap for what I did, but it paid the rent for a 19 -year-old party-kid for a while. The boss eventually moved out to the Central Valley to get away from Bay Area traffic. I helped him move the place, and hung-out at his place keeping production rolling with his wife and son for a couple of weeks while he got set-up and hired some new help. (Didn't go bar-hopping on my 21'st b-day, either, but the bosses' wife made a swell cake.
)
He tried REALLY HARD to convince me to move out to Modesto and keep on working for him. Apparently I have the touch. But I was a home-body without even a car of my own, just a bycicle, plus I rather like the S.F. Bay Area, liberal swamp that it is.
So THAT background qualified all that stuff I wrote. I know how stainless handles, how it works, on a rather intimate level. Stuff gets downright ornery, sometimes. Pulling T's and crosses out of tubing hydraulically can set up some powerful residual tensions! And you woundn't think a 1"-thick steel disk would "relax" out of flat just by skimming 30-40 thousandths off of one face.
So on the one hand, you could see how I could be "done" with stainless steel. I've certainly bled enough over it. On the other hand, I also really like the stuff. I like it's look, luster, properties and strength. I even have a bunch of stainless guns, although I never bought 'em BECAUSE they were stainless. It just qualified as a minor feature not even meriting the dignity of a reply.
What can I say? I got a bee in my bonnet, and decided we needed some righteous good discussion to liven up the place. I TOLD you my head got swollen, so please forgive me if I blocked the light, or something.
At least I wasn't comparing calibers. Heck, I staked out a definitive position instead of asking questions or opinions. Bold as brass, me. On occaision, when I desire other's opinions, I shall deliver it to them.
(But mete didn't tell me I was full of it either, so maybe I do know a little something. Perhaps I shouldn't sell myself short, here.)
This is also making for some very interesting reading. I live for gun esoterica. Metallurgical properties as considerations to bear in mind whilst designing major operating components definitely fiits the description.
To be relevant to the discussion at hand, most of the porosity references I've come across were in discussions about nodular cast-iron combustion-engine components like crankshafts and blocks, but nodular cast-iron is a long way from modern alloys. On the other hand, my understanding of metallic grain structure and the effects of heat-treatment to said structure in terms of grain-growth and composition-change comes from the same basic premise.
Do the alloying elements like chromium and nickel in modern steels eliminate the "pores" by "filling the cracks"? Or do they allow the idividual bonds of the metallic ions to form a closer, tighter, more uniform crystal structure with a regulated sizing, filling the spaces by the consistency of the size of the ions, like consistently-sized bricks in a wall?
Or perhaps it's niether of those? I could be totally off base, here. Chemistry was a long time ago. And being told about ionic bonding failed to impart an understanding of the physical relationship of the elemental components involved.
And presuming I'll even understand the answer. I'm not to sure about the question!
