A lot of folks like the 7.62x39 mm but I think its a bit overhyped due to the mystique of being Soviet and us having been on the receiving end.
(Here is a quality analysis of effects on humans of both rounds by a trauma MD:
http://www.thefirearmblog.com/blog/2016/01/01/spec-ops-doctor-rather-shot-with-ak-47-over-m16/ )
It's not a bad round and has its roots in the german 7,92 Kurz round (the comma is not a typo) but the 5.56mm and the .223 Rem shoot much flatter which results in better accuracy and some say better effects.
Now the combloc
may be less deflected by bushes/shrubbery but that its only superiority which is ultimately why the Soviet Union switched to 5.45mm a round from a similar design concept as the 5.56.
still nothing
wrong inherently with the 7.62 combloc.. but since our ammo importing laws have changed the big cost advantage is gone.
Otherwise I would be all over a AR47 marrying the ergonomics of the AR platform with the cheaper round.
Back in the day a 7.62x39 mm round could be had for 8 cents a round or even less.
But now they are the same price as 5.56/.223 Steel cased ammo.
And this common round, does like I said, shoot flatter and will also be more readily available due to battlefield pickup
(there are exceptions to what you might do...Having said all that if I had a team at a BOL and was maintaining many firearms for a group (not that I am
) I would consider stashing one 7.62x39mm caliber rifle so we can make use of a windfall just in case we ever stumble on someones a huge surplus 7.62x39 stash via battlefield pick-up...)
But If I am equipping myself or maybe just 1 or 2 other guys I'd stick with the 5.56/.223 caliber rifles.
I admit there are many schools of thought on this and not all will agree with me but as a former Combat Developer and Operational Concepts Writer for the Joint Force I trust my ability to conduct a rational-all-things-considered analysis based on our given non standard operational environment as Preppers.