As a replacement to the M1 carbine for non-infantry troops, the 5.56 m4/16 is a solid improvement -- in most instances a more effective round especially if just exclusively fmj, and the AR is pretty well sealed from elements and dirt with mag in, muzzle condom on, and dust cover closed so with limited use and infrequent cleanings, whether stored on rack or carried for security/perimeter patrols, it should work when needed. That's probably a lot about why the US Air Force was the first to adopt...
As a general purpose military front line infantry carbine/rifle I find 5.56 lacking... Logistically, however I don't see the need for a full-sized .308 rifle in most types of combat... Double weight of .308 rounds vs 5.56 just doesn't make sense when one looks at how bullets are expended in combat zones.
Militarily, most small arms fire is intended for suppression and fixing the enemy, so odds of a given bullet actually hitting an enemy soldier is low.
This marine document on the depuy fighting positions, has a stat of 12 kills per 100 rounds fired for defenders shooting from positions of cover, pretty much a best-case combat scenario:
http://www.2ndbn5thmar.com/fight/whythedepuyfightinghole.pdfIn Afghanistan, the GAO estimates US troops fire 250,000 rounds for every enemy insurgent killed -- that's about $75 grand in ammo costs (by commercial bulk retail pricing) BEFORE you account for the abhorrent costs of shipping anything to and within that country:
http://www.belfasttelegraph.co.uk/news/world-news/us-forced-to-import-bullets-from-israel-as-troops-use-250000-for-every-rebel-killed-28580666.htmlBack to the original point, while yes the .308 is more powerful, within 250-300 yards the 7.62x39 can do pretty much everything .308 can do and often better, with perhaps a small exception of .308's greater penetration against steels solely due to higher velocity. .308's energy inside of 250-300 yards generally is too much power and results in much longer penetration necks in gelatin with similar issues to the m855 ammo with through and through pencil holes with little energy deposited in the enemy -- yes .308 is a 30 caliber hole in this instance vs a 22 caliber pencil holes for 5.56, but insofar as pencil holes'/permanent cavity there shouldn't be much difference between a 9mm round and a .308 going through and through, the temporary stretch cavity is where differences come in.
While in the weeds, the main point here is that if anticipating a substantial amount of engagements beyond 300m, .308 shines. If anticipating most to all engagements within 300m, then 7.62x39 shines. Most folks who deem the .308 caliber/rifles to be paramount for combat have an argument that essentially distills down to that they'll pick off their foes at 500 yards (or other extreme range) -- which doesn't really account for the fact that no human will willing be a sitting duck so will seek cover/concealment, the likely limited marksmanship of most of these types including the challenges related to ranging and limited exposure of enemy once they know they are in the crosshairs that won't allow multiple shots at same target at same place (it won't be a static range), etc...
Back to the military, m4s are primarily used for combat at distances where supporting/combined arms cannot be used -- whether unit rifle grenades and mortars, supporting artillery, or air, troops typically can and are taught to engage enemy at range with these assets and small arms merely use to suppress and pin down the enemy to be killed by methods other than small arms...
And even in the small arms realm, individually portable squad automatic weapons are considered the primary tool for enemy engagement... But with most US infantry now being vehicle-borne troops, .30 and .50 cal vehicle mounted machine guns and grenade launchers typically are used in place of or preferable to M4s for engagements at all distances...
When you're talking about danger-close grenade range combat, the M4 and 5.56 round does perform sufficiently in most cases...
Also worth noting that modern small caliber high velocity rounds with shorter effective ranges have been outgunned by old bolt action rifles in service calibers in Afghanistan, primarily a matter of range, but worth noting...
http://cominganarchy.com/2010/05/21/it-took-us-nine-years-to-figure-this-out/http://archive.boston.com/news/world/asia/articles/2010/05/21/us_rifles_not_suited_to_warfare_in_afghan_hills/Ultimate point here is to have at least a high-level understanding as to all the ways and reasons compromises are being considered. For the military it's seldom about the "best" but rather about logistics, procurement, and pacifying the bureaucratic officer corps and all the varying stakeholders that have different priorities than optimal terminal performance, weapon reliability, etc...
All considered is why that while 7.62x39 weighs ~45% more than 5.56, it's potential to be more effective, require only one shot to put an enemy out of action vs a couple shots with 5.56, better in short barrels, cases chamber/extract more reliably, etc, just aren't a primary concern...
*stealing ammo weights from here:
http://forum.saiga-12.com/index.php?/topic/65272-how-does-weight-compare-between-steel-case-762x39-and-brass-223/200 rounds of steel-cased 7.62x39 122 grain weighs 7.22 lbs. (1000 rounds = 36.15 lbs)
200 rounds of brass-cased .223 55 grain weighs 5.02 lbs. (1000 rounds = 25.13 lbs)
200 rounds of 2 3/4 12 ga 00 bk weighs 19.18 lbs. (1000 rounds = 95.90 lbs)
200 rounds of 7.62x51 146 grain weighs 10.86 lbs. (1000 rounds = 54.30 lbs)
The figures for the 7.62x51 was supplied to me by someone else so I can't guarantee it's accuracy but it seems right to me. The other calibers I personally weighed so they are accurate. The difference between the 7.62x39 and .223 is about 2 lbs. The figures kind of screw up the idea of carrying around thousands of rounds on foot.
From a civilian, for self defense within 100 yards (unless your part of the country has frequent gunfights, should cover all legally justifiable self-defense scenarios -- at least before the zombies come), 5.56 is an adequate performer especially with premium non-fmj ammo. It also generally produces less recoil, is lighter, is a more compact round, and in the VZ58 uses AR mags, which are almost as awesome as glock mags.
But again, 7.62x39 is better for hunting, barrier penetration, and as a combat small arm at carbine (~300 yard or less range), especially if you don't have mgs, supporting arms, etc, like the military does...
Define your needs and make a choice -- any gun is better than no gun. There's no wrong answer, just differing opinions -- but those whose opinions' differ may decide your opinion/decision is wrong... haha
