Receiving End

Something I don't see cited much concerning the lethality of 5.56x45mm is that the Russians copied the idea.

Vietnam provided lots of data for them to see if their round was better or worse than ours.

In 1974 they adopted a new version of the AK in a new round.  AK-74 and 5.45x39mm 7N6.

Because they're damn good at espionage, I suspect they had access to our data from Vietnam about the effectiveness of the 7.62x39mm M43 round.  Their picture of the comparative effectiveness is more complete than ours, really, because of our ongoing frustration about the NVA removing their fallen from the battlefield.

5.56x45mm M193 is actually a proven killer.  5.56x45mm M855 works too.  M855A1 should be even better from looking at the construction of the round.

They're all better killers than heavier rounds when you click it into our doctrines.  Past a certain range, it is not a rifle problem, but an artillery one.  Whether this is a sound doctrine is the real debate and if the range where the mortars take over for the rifles is longer, then something like 6.8 or 7.62x51mm would be more appropriate (depending on how much longer).  The debate about doctrine has to include a discussion about whether we're going to have the riflemen engage at ranges where they're supposed to be letting the arty or CAS take it.  Some of our anguish is being caused by taking shots at ranges the gun can't do the job at.  Ranges where the old 7.62x51mm guns would be working fine; but I alluded to something in an earlier post, the average grunt with an issue rifle can't really wring out the performance we're asking of them here.  A lot of the ineffectiveness of 5.56 can be safely attributed to didn't hit anything; and that grunt would miss with a heavier round too.

The Marines might be on a better track than the Army with universal issue of ACOGs and retaining the 20" barrels on their M16A4.  Canada's C7A2 has magnifying optics and the longer barrel as well, and there's no controversy from The Great White North about their small arms choices.

But inside a certain range, a hit is a hit and dead is dead regardless of which NATO rifle round used.