"Are these pictures of a safe condition?"
Possibly, trending towards probably (more on that later)
"The Pedersen block was NOT in the fully forward position when the gun discharged."
Absotively
"the Remington 51 (the original) CANNOT discharge unless the slide is fully forward. This is not true of the R51."
Indubitable
The R51's out of battery safety is the trigger disconnector (a kind of odd way to achieve this, compared to a firing pin safety, but it's cheaper and theoretically works), which I've detailed at length as being possibly the weakest of weak links in the R51 (chamber cut is the other). The way it works makes it very susceptible to poor manufacturing; the enlarged pin slots and poorly-stamped cam lobes mean its engagement position will vary quite a bit, gun to gun. On my gun, at least, the hammer can drop for nearly the whole portion of slide travel
before the block is raised. That means my gun can fire with the block pushed all the way back against its stop.
This is
not necessarily an unsafe condition. What it is, is a condition of weaker case head support, which as we've seen with Glocks, is
not necessarily a deal-breaker. As you saw, ROH, the gun was not damaged nor did it fail to fire in an unsafe way --the case did not rupture. While it is certainly unacceptable that the chambers were so poorly miscut that some rounds will fail to fully chamber and fire in such a state of poor case support
it has not at this point seemed to have resulted in a catastrophic or truly dangerous failure for anyone. Given the Internet's appetite for beating on the R51 since its flop, I find it hard to believe that such incidents would go unreported, more so if they occur with any frequency. "R51 Kaboom" still just chases up MAC's "Is the R51 Safe?" article, which suggests to me the question is still a question.
It is inexcusable the guns were so poorly made that they can function in so compromised a state that the brass bulges worrisomely (and that the firing pin is so large in diameter,pointed in shape, and light in weight, that every. single. last. round. in my R51 shows the same unruptured "pimple with a dimple" that you show, there, regardless of ammo used). But that is not the same as the guns being unsafe to fire (to defend your life with, maybe), until we have some cases of actual unsafe failures. I think we had one person mention a low-pressure primer pierce and pin-hole case failure (both of which are worrisome and indicate a close margin, but were not dangerous failures), but that's it. The old
Rain Man Quantas axiom, "never crashed" applies here; there's nothing special about the airline that made it safer, but the fact was they
had never had a crash (still haven't, I think
)
I'm jealous of how smooth your chamber appears to be. Mine was so rough that the cases looked like they'd been pulled through 60grit sandpaper when extracted; striped and frosted texture. FWIW, MAC had a very similar OOBD (with +P ammo, no less) and his case looked identical. IIRC, he remarked that the recoil was harsher (makes sense for a block fully back, with no take-up to smooth the impulse), and the gun was locked up by the bulged case. Does this differ much from your experience? It may be your brass was further from the knife edge than you might think (still not acceptable performance, though).
TCB
Why can't I predict anything I can actually profit from? 
I agree that it's a good design ... but I really think Remington ought to step up to the plate and do it right, which would avoid an infringement on patent/trademark/copyright (?) *legal* 
