So I see Ilford still offers 70mm HP5 film stocks. Perforated and not perforated. Will either of these film stocks work with a 1968 vintage Hasselblad 70mm back? I bought a mint back, mostly because it was cheap and looks cool. I have a darkroom and big enormous Nikor reels and a non-daylight tank.
I have no reason to do this, but like Mt. Everest...............
Are the metal cassettes reloadable? Which film? Perf or non perf, or is it even possible?
Ilford still does the annual ULF orders, which is most likely what B&H is doing since Ilford doesn't produce 70mm outside that once a year window in so far as I know.
There's also Rollei Ortho 25 for significantly less (<$100 USD) from Europe.
Rollei 400 was available up until recently, one user from RF forum reported Macodirect is no longer stocking it.
Beyond that, you can go for some Kodak movie film, surveillance film, or expired stock obviously.
All 70mm cassettes I've seen are reloadable (Kodak, Hasselblad, Linhof, etc).
Perf or non-perf depends on the back. Linhof, Pentax and Hassy backs all have sprockets and cannot shoot non-perf without modification.
There's an official gasket replacement wheel for the Hassy backs to convert for non-perf, which is difficult to source, or you can make your own.
Most other backs I've seen are non-perf, which use a friction based advance so you can use perf or non-perf in those (e.g. Graflex, Mamiya, etc)
Then there's all the oddball stuff like Keith backs, and military (e.g. Fairchild, Graflex, etc) cameras that were designed for 70 mm. Most of these require loading the film on the original 100ft spool though, save the KS-6.
There are 2 kind of 70mm backs, the 100-200
and the 500:
I assume you have the 100-200. The 500 ("intended for large scale film consumers") is probably a pain to use (needs a battery) and carry around. The applications it was targeting are probably better served by digital nowadays.
Not trying to split hairs, though there were a lot more than two types of 70 mm backs from Hasselblad:
70/456 (this one was special order only)
* I've seen a couple variants of the 70/500, though nothing from Hasselblad giving them officially separate designations.