I've reloaded plenty of 7.62x39mm. The polymer steel-cased seem to be a bit more rust resistant, but I've reloaded Yugo, Lapua, Norinco, Silver Bear, Golden Tiger, you name it.
I've found most berdan cases will deprime quite easily with water. If you don't have a decent seal with your Lee 30 caliber punch (sans pin; you surely have a broken one lying around), just use a plastic bread wrapper. If really looking to burn the clock, neck size them before decapping. If you have a slightly larger diameter punch, you should do fine with fired cases with no plastic or sizing.
If you have a few stubborn ones, just cull them from the mix. Yugo 8mm and South African .308 tend to be stubborn. Forget French .30-06!
The RCBS decapping tool works okay, but adjust it properly, so you don't damage the anvil or snap the cutter. It isn't that cheap either.
The flash holes are quite tiny, so it would be hard to make a twin punch tool that would last very long, I suspect, let alone align properly with every brand of case.
Berdan primers are hard to come by in the USA. Murom makes them, but try to find a source for them.
I am not that ambitious to machine the primer pockets to accept a boxer primer, whether with glue or with a spent berdan primer reamed to spec.. I know some folks remove the anvil from boxer primers and glue them into the primer pocket. Most 7.62x39mm berdan primers are .217" diameter (boxer LR are .210" dia.).
I used to shoot matches with a couple that had Mini-30s and they only used Winchester ammo. They apparently made the big bucks, didn't reload, so they welcomed me to scavenge their brass.
Why reload such an inexpensive caliber? I guess, because I can. It's also fun using other bullet styles, cast, plastic, frangibles, sabots etc. try finding these at your LGS or favorite mail order house.
Cheers!
Oops! Left out the link. here it is again for the fifth or sixth time...
www.mpzflame.ru
Also, in addition to the video above, you will also find some berdan cases with one flash hole (mostly Romanian 8x57mm, I think).
I've reloaded berdsan-primed .303 British, 7.5 MAS and Albanian 7.62x54R (brass and has a .217" diameter pocket). Romanian (steel), Turkish, German, Yugo 8mm.
GP11 Swiss decaps wonderfully. Not all of the aforementioned calibers use the .217" diameter primers, but those that do, you may find LRB primers for such uses.
In the past, Grafs and Powder Valley carried the LRBs, whether packaged under the Tula, PMC or Murom label.
Picture is not 7.62x39mm, but you get the idea.