When To Choose A .308 Over 5.56?

[Fox33]

So just back from Govt' sponsored tourism.....

#1 Failure... that is a nice rig... but I must ask the advantage of folding irons vs. a red dot @ 45 (which is how I have been doing it)

#2 Caliber is important, but environments drive your situations, and situations drive your tactics. When I think of tactics I think of who is trying to apply what and where. The who and where I see as the big factors in this discussion. Distances have been the focus of the discussion and I'd agree that they are the #1 factor in caliber selection. Smaller is easier closer IMO.

Another factor has to be looked at that is often overlooked in this discussion. Flexibility

I find 7.62x51 is much more flexible than 5.56 as it has a greater variance in configuration. I see these wars we've been fighting as not winding down, but spinning up. With the Russians and by proxy the Chinese developing new body armor designed to protect against 5.56, the current stop gap is 7.62x51. Handl Defense has been in talks with some people who worked on the last caseless project for HK and I sat in on the conversation. I am convinced that Small Arms has to change and the brass cartridge, impact primer, and copper case bullet is where the change starts.

But for now; if I want to punch steel/plate with a 180gr AP, I want a hollow point boat tail 175gr sub MOA round, 110 or 130 gr defensive round for soft targets, or even API, I can do this all with 7.62x51. These rounds are also available in platforms that can be used in a CQC environment or in a DMR setup. Yes this can be done with 5.56, but not to the same effect. When it comes to terminal ballistics its not even close.

#3 the other part of this discussion is who. I think 5.56 was selected for many reasons like when zeroed @ 25m the POA-POI is very close to the same as 200m. This means without discussing ballistics to draftees, you would have the greatest possible effective hits with the least amount of training. Zero it and point to shoot, for what is considered pretty much max range for a nug to shoot out to.

For the most part the admin chick who weighs a 100lb is not going to wield the SCAR H or HK 417 very effectively. Many of the limp wristed, fat, xbox drones we are going to end up drafting once a city or two gets hit with weaponized bubonic plague ISIS is working on, are not going fair well with it either. So maximize the effects of 5.56 but leave the killers a real option. Right now the only one that can do it all is 7.62x51

[Failure2Stop]

#1 Failure... that is a nice rig... but I must ask the advantage of folding irons vs. a red dot @ 45 (which is how I have been doing it)

Because I run a 1-8x, primarily set on 1x, spun up as needed.
An event that crashes my 1-8 is probably going to crash any other glass aiming device, in which case the irons will work well enough to let me do what needs to be done.
I've had temperature changes fog up lenses, non-transparent liquid occlude shooter-side lenses, and salt spray evaporate away leaving lenses covered. All of these events would effect all glass, none would make an iron unusable (though you might need to blow the aperture out).

I do have to disagree with your #3 point: a 25m POA/POI is more like a 400 yard zero with 5.56 from a 20" barrel.

[Koshinn]

With the Russians and by proxy the Chinese developing new body armor designed to protect against 5.56, the current stop gap is 7.62x51.

Level IV body armor, the kind I'm sure you were issued, is rated to stop 30-06 AP at the muzzle. Body armor isn't some state secret, it's available for civilian use. There is literally no way that both Russia and China haven't had body armor rated against at least M855 for decades, and likely 7.62x51 as well since that has been in NATO usage for more than 50 years.

If we're talking about armor, you're probably not going to see much of a difference between 5.56 and 7.62, if any at all.

[henschman]

5.56 is great for home defense and a general fighting rifle from CQ to mid range. It can certainly deliver hits at longer ranges, like 600-700 yards, especially with heavier OTM ammo, but I don't think anyone would make the claim that it is optimal for this role.

7.62 is basically the opposite... it is in it's element for mid to long range shooting, and is a lot easier to shoot in the wind than 5.56, but can do short range and CQ in a pinch. It also offers much better penetration of hard barriers.

The 5.56 is the better choice for an overall fighting rifle IMO, because most fighting happens at closer distances where it is in it's element, yet it can still get things done out farther if need be; and it is plenty ballistically effective with good ammo choice (and not too bad even with cheap ball, due to fragmentation). Also a full 30 round mag of 5.56 weighs almost 1/3 what a full 20 round mag of 7.62 does, so you can carry a lot more of an ammo loadout.

The 7.62 is a good choice for a DMR type setup, and would be good for running far ambushes and that sort of thing, where you are going to be intentionally engaging from some distance, yet can still take care of business up close when called for. It is also a great hunting round. With hunting, getting a one-shot kill and dropping the animal right where it stands are much bigger concerns than with the fighting role. You are also worried about keeping the meat intact, which fragmenting loads are not conducive to... with hunting you use rounds designed to expand and penetrate, to cause the biggest wound in a vital organ as possible, with the greatest instant drop in blood pressure possible, to put the animal in shock and drop it where it stands. A full power .30 cal just does this better than an intermediate power .22.

FYI with 55 or 62 grain ball, a 14.5" AR carbine zeroed at 25m will have something like a 320m far zero. A 7.62x51 rifle with 147 grain ball and AR-height sights will do about the same. 55/62 grain 5.56 and 147 grain 7.62 have very close to the same trajectory out to 600 yards. A 50 yard zero will give you right at a 200m zero with either one.

[Failure2Stop]

Level IV body armor, the kind I'm sure you were issued, is rated to stop 30-06 AP at the muzzle. Body armor isn't some state secret, it's available for civilian use. There is literally no way that both Russia and China haven't had body armor rated against at least M855 for decades, and likely 7.62x51 as well since that has been in NATO usage for more than 50 years.

If we're talking about armor, you're probably not going to see much of a difference between 5.56 and 7.62, if any at all.

M993 is actually pretty good:

3.5.7 Penetration. For each test below, the projectile of the cartridge shall penetrate 7mm thick High Hardness Armor (HHA) plate, in accordance with MIL-DTL-46100, creating a hole through which daylight can be seen.
3.5.7.1 Penetration at 546.8 yards. The bullet of the cartridge shall be capable of penetrating the HHA plate at 0 degrees obliquity at a minimum range of 546.8 yards (500 meters).
3.5.7.2 Penetration at 716.3 yards. The bullet of the cartridge shall be capable of penetrating the HHA plate at 0 degrees obliquity at a minimum range of 716.3 yards (655 meters) with a success rate of not less than 50%.

Basically twice the performance of M995,

3.5.9 Penetration. When fired at 0 degrees obliquity, the bullet of the cartridge shall be capable of the following penetration requirements:
Material and thickness Range Required penetration
3.5mm NATO plate 656 yds (600 m) 50%
12mm steel armor plate 109 yds (100 m) 100%
1/2 inch aluminum plate 492 yds (450 m) 50%
1/8 inch steel RHA plate 601 yds (550 m) 50%
Hollow concrete block (through both sides) 54.7 yds (50 m) 50%
1/4 inch steel RHA plate 437 yds (400 m) 50%
3/8 inch steel RHA plate 262 yds (240 m) 50%
1/2 inch steel RHA plate 164 yds (150 m) 50%

Which is distinctly better than M855:

3.9 Penetration. The bullet of the sample cartridges shall demonstrate complete penetration of 10 gage (.135 inch) thickness AISI 1010 to 1020 steel plate target with hardness between RB 55 minimum and RB 70 maximum (NATO plate) positioned at O + 5° obliquity and located 656 yards (600 meters) from the weapon.

(All of the above is open-source information)

[Hot Holster]

5.56 for general shooting and coyote's.

300 Blackout 9.5" suppressed for HD/SD, and hog hunting out to 150 yards or so. Barnes black tips for supersonic, Lehigh Defense 174gr controlled fracture or 194 maximum expansion for subsonic use.

.308 when I need to reach out longer distances and slap something nice and hard.

[markm]

If we're talking about armor, you're probably not going to see much of a difference between 5.56 and 7.62, if any at all.

Yep. 7.62X51 is much easier to stop than M193 or M855 in an armor sense. It's so much slower. I used to get a kick out of guys shooting my gongs with their .308s... They'd often think that it would some how punch through...

[Failure2Stop]

Yep. 7.62X51 is much easier to stop than M193 or M855 in an armor sense. It's so much slower. I used to get a kick out of guys shooting my gongs with their .308s... They'd often think that it would some how punch through...

Let someone with M993 shoot those gongs and you might reconsider.

[Fox33]

Let someone with M993 shoot those gongs and you might reconsider.

exactly, it was I was getting at.

BTW guys I have been trying to find the info about the new russian body armor. There is an open source document that talks about it. It came out around the time of the Russian UW operation to take the Crimea. That it was specifically designed to protect from 5.56 AP. Once I find it I'll post it up.

[TehLlama]

Let someone with M993 shoot those gongs and you might reconsider.

I've seen the half-inch steel targets perforated enough to believe it'll have an effect on the other side of armor - that said even for the anti-personal body armor application, I'd rather have a smaller caliber with more rounds and hope I can connect multiple times instead of relying on one hit to completely incapacitate (it's not as though anybody on the other side of that rifle plate is fighting at 100% effectiveness right after that armor makes itself worth its weight in platinum). AP 308 isn't exactly common in my neck of the woods, the place I really see for that ideally would be in an MMG at a vehicle checkpoint as primary application over running it through a shoulder fired system (nice fallback ability, but for most of those uses a useful barrier blind load is probably so much better across the rest of the performance spectrum that I'd rather run that).

There is a weight/OAL range that .308 general purpose carbines can work in - 16" somewhat light carbines with lithe accessory sets (the ACC looks to be the standard bearer in this regard) and a good variable optic can put a well-sorted GP-308 into the discussion, but it still won't reach that handiness factor of a simple LW 5.56 carbine with red dot/light/sling and little else, so to make sense (having a longer reaching performance envelope plus carrying more impulse) for the tradeoffs (cost, lower magazine capacity, OAL, etc.) : they need fairly high quality barrels in non-pencil profiles, non-boat anchor handguards, and a properly dialed gas system or else it becomes a pricy hot mess of disappointed customers - even the SCAR-17 suffers from a lot of this.

Those bits of information plus the possibilities with a smartly set up 300BLK setup (again, those shine in 8-10" barreled suppressed setups) that there is a zone where .308 setups don't make any sense at all (12-14.5" 308 carbines have been basically universally figured out as dumb with a couple odd exceptions) because at the lower velocities, a BLK setup with a couple more inches of barrel (offset by the receiver length) can net comparable performance with similar projectiles. On the suppressed minimal OAL setups, BLK or 5.56 just makes more sense. On the other extreme, lower drag coefficient calibers (6.5CM excels at this task) through longer barrels (20" and bigger) and the .308 options don't exactly excel when compared to those other options, so this leaves a sweet spot of 16-18" .308 gas operated semi-auto setups for general use carbines being awesome, and everything else tried with those setups are basically outclassed for the money.

For me, the niche I want to fill with a .308 weapon is to have a solid, reasonably light, sorted semi-precise 16" suppressed setup (short 7" Ti can) - for terminal effectiveness and accuracy beyond the optimistic 600m envelope of my SPR/Recce setups when equipped with Mk262 clone ammunition, and hopefully the ability to hit ~2MOA targets with some consistency out to a click.