The .308 is a good round, but it won't go through all armor.
This guy claims the Dragon Skin can take a 7.62x54:
"Ive also firsthand witnessed during the push in Fallujha, a guy take a sniper shot from a Dragonuv (7.62x54) from a 7th story window at a much steeper angle than 20 degrees, it put him on his ***, but didnt penetrate at all."
http://www.calguns.net/calgunforum/showpost.php?p=2102380&postcount=44
It's very likely that dragon skin can. Basically anything that can take a 7.62x39mm at point blank can take a .308 at 100 meters or less since the .308 starts with more energy but loses it very quickly. The 6.5mm Grendel has more energy than a .308 at any range greater than 100m, simply because the Grendel starts with less energy, but has such a low drag coefficient that energy isn't lost quickly. Unlike any other modern "assault rifle" rounds the Grendel aims to preserve energy rather than require more of it. The 6.5mm Grendel is a 7.62x39mm round necked down to 6.5mm and topped with a 65g bullet which is still supersonic at 1000m. The 5.56 platform's max effective range on a point target is 500m, the 7.63x39mm is 300m, the Grendel is 1100m.
jkm1864 said:
This is the reason why I have a M1A, AR15, SKS, & GSG-5. I have many guns for many jobs. I would use my AR15 with a scope for accuracy but if I needed the punch I would use my .308 hands down. The .308 will go slam through a rifle plate where a .223 & 7.62X39 will be stopped.
What I was driving at in my previous post was that the future holds one "mission adaptable" gun, one platform, that performs all these jobs. A modular design approach allows manufacturers to produce a "platform" which is comfortable, railed out to support "bolt on" accessories, and ultimately uniform in practice and use.
As a reloader, and one who is "up" on current ammunition specs, the .308 ball (7.62x51mm) round has the same chance at penetrating SAPI plates as does the 7.62x39mm. The only differential is the distance the round is fired from. Neither of these rounds will penetrate SAPI plates from any comfortable distance. The .308 is just as powerless as the 7.62x39mm when it comes to the penetration of SAPI armor.
There is, on the free market a brand new class of rifle which will let you choose how and when it used. This new class of rifle is modular in design, which allows the end user to choose the caliber, ammunition type and disposition of the weapon when used. You best bet is to roll with a multifunction rifle.
In the civilian market, unless you have some pre-formed steel penetrators, or a basement or cache full of "black tip" (Read NATO Armor Piercing {AP}) ammo, then heed this advice.
Armor piercing ammo, of any type can go for as much as $25.00 a round. You're best is to learn the reloading trade and make friends with those who know the swuagng trade. Learn how ammunition does what it does, and how "government only" ammunition accomplishes the goals it was designed for. After that, it's easy as pie, with the appropriate equipment and skillset to reverse engineer rounds rounds slated for "government-LEO ONLY", perfectly legal like, in your own garage, for pennies on the dollar.