excop: As to lethality, you are ignoring the difference in caliber. The 7.62x39mm round has a lot more stopping power at close range than the 5.56mm round.
Affecting lethality, the ar15's smaller caliber doesn't matter that much compared with the ak47. Lethality is if the target dies, not instantly but within a few minutes or even later.
The ak47 with the larger bullet (twice as heavy) has greater stopping power in it will stop (immediately bring down) hunt animals & people, better than the ar15, but the ar15 might leave it's target up & walking about while mortally wounded, bleeding out for instance. Taking into account more accurate shooting, the ar15 would work better for mass shooters (which is why I support banning ar15s, as well as ak47s et al).
The ar15 bullet (0.223fmj) tends to fragment into two a few inches after penetration, & can cause cavitation in each of the two wound patterns, causing twice as much internal damage to surrounding tissue as the ak's 7.62. The 7.62 will not fragment as readily as the .223 (tho it can of course, hitting bone etc), leaving one wound pattern. 7.62 can cause cavitation of course.
The recoil difference you mention is negligible.
If the 1962 test remains fairly valid, 33% more recoil in the ak47 is 'negligible'? a third more doesn't seem to fit the realm of negligible, and it's a cumulative effect, per bullets fired.
Were I to chose a weapon for close in lethality, hands down the choice would be the AK.
Fine, but you realize a solid portion, if not most, of shooters would take the ar15 or m16, don't you? lighter weight is a boon.
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