In the older school of thought that favored fragmenting 5.56 rounds for all-purpose defensive loadings, the advantages of calibers such as the 6.8 were concrete and significant.
A) Fragmentation was the key to ideal wounding, and fragmentation range increased dramatically with the larger calibers at a given barrel length.
B) Larger calibers such as 6.8 SPC defeated barriers that OTM and FMJ 5.56 rounds could not.
The new thinking seems to be that barrier blind 5.56 rounds such as BH 50 grain TSX should be employed for general use. They maintain ballistic performance out to 300 yards, which largely negates the range issue. They also defeat commonly encountered barriers, unlike their OTM and FMJ cousins.
If we accept that their terminal performance (expansion to ~.45" and a large, consistent, early-forming temporary cavity that wounds inelastic and fluid filled organs such as the heart, kidneys, and liver) is adequate without fragmentation, is there much of a point to larger calibers such as the 6.8 anymore? Or has this become more of a marginal, incremental paradigm such as the 9mm vs. .40 S&W vs. .45 ACP?
Hmm. Interesting theory. Id be inclined to believe that with good barrier blind loads that the slightly larger intermediate sized cartridges dont offer much over the 5.56.
Intermediate calibers that fit the AR15 magwell do not exact the carry weight penalty of .308 ammo (not even close) and obviously do not need the heavier and larger AR10/SR25 platform.
dont forget that the 6.8 also has extended the effective range of the carbine as well as the terminal ballistics.
better 5.56 bullets are really just a patch for it’s inherent deficiencies. It works, but it’s still subject to the laws of physics and momentum. Heavier, still breaks thru stuff better.
I’ve been debating this myself. By all means of measurement, ie terminal effects and barrier testing, the 6.8 is superior to the 5.56 in every way, and is a much more manageable carbine choice over the .308. It is just unfortunately that the 6.8 lacks any wide spread adoption. I would also like to see a lower receiver specifically designed for the 6.8 so that the magazine well can be wider and accomidate magazines on par with PMAGs instead of the thin steel walled magazines available now.
Lets not forget that the 6.8 is in itself a patch which operates within the limitations of the AR-15 platform. If we had something like an AR-12.5 that provided a longer magazine well, and action than the AR-15, but still shorter than the AR-10 we could start getting rifles that are optimized for the 7 X 46mm and other true intermediate cartridges.
Considering all the gear many people hang off an AR-15 a naked AR-10 like a Larue PredatAR .308 doesn’t really weigh any more. As far as ammunition goes I don’t see ammo weight being an issue for civilian or even LE tactical usage. The tradeoff between firepower, and mobility is always a consideration. .308 still holds a significant advantage over any of the other common service rifle calibers as far as terminal performance, and intermediate barrier performance. The user must of course determine if the added recoil, weight, and expense is worth the increase.
I think I mentioned this before… A review the ballistic gel data on Hornady’s LE website shows almost identical performance between the TAP 6.8 110 BTHP and the .308 155 gr TAP while the 168 gr BTHP is worse than both previously mentioned.
While the 6.8 mm 110 gr OTM offers excellent terminal performance that is better than any 5.56 mm load, the 155 gr TAP in those links is creating a substantially larger wound track than the 6.8 mm.
If that’s the “new paradigm” I’d abandon 5.56NATO tomorrow. Fortunately, it sounds like a temporary fad that shouldn’t last too long.
One of the big selling points, in my opinion, on the 5.56NATO cartridge is that it has excellent terminal performance on a “primary target” (the person you are exchanging fire with) but has a reduced risk of stray rounds penetrating through common materials and putting innocent bystanders at risk.
The other big selling point on the 5.56NATO is the fragmentation it exhibits in tissue. It is a very effective cartridge at causing damage to the human body.
For law enforcement and the defense-minded citizen this is an advantage. Obviously, your trade-off is that you lose some ability to penetrate barriers that your opponent may be using as cover or concealment.
To me, losing the two biggest advantages of the 5.56NATO to basically revert to a glorified 7.62x39mm that is accurate at longer range is… I really can’t believe we’re even having this discussion. It is so far out of the realm of anything I’d even begin to consider a good idea.
In the above photos of bare gel test shots by three different calibers, all three projectiles offer adequate penetration depth, however the .308 155 gr AMAX is creating the most tissue damage, followed by the 6.8mm 115 gr OTM, then distantly trailed by the .223 75 gr OTM. One of the largest SWAT teams on the West Coast has used both the .223 Hornady 75 gr TAP and .308 155 gr Hornady AMAX for over a decade; the post-mortem forensic results of OIS incidents demonstrate substantially more tissue damage with the .308 AMAX projectiles compared to any .223 loads.
I am quite aware of the penetration capabilities of .223 projectiles through building materials; in fact, I believe we wrote the first papers discussing post intermediate barrier wounding effects back in the late 1980s at LAIR and early 1990’s with the IWBA. Likewise, Dr. Fackler, the director of the LAIR wound ballistic laboratory, was the first individual to accurately describe the fragmentation effects of 5.56 mm projectiles in tissue back in the mid-1980’s.
I am sorry you can’t believe we are “having this discussion” and that it is “so far out of the realm of anything I’d even begin to consider a good idea”; I suggest you revisit the past 25 years of wound ballistic progress and try to envision that perhaps technology has improved and there are better options available now.
I’m curious at what point that the 762x39 became a poor combat cartridge myself.:blink:
The ONLY real selling point of the 5.56 AT THIS POINT is that it is cheap and ubiquitous. Every other feature of the round can be had in a better cartridge of some sort.
-you want frag? get a frangible or varmint round
-Barrier pen? copper or bonded
-AP? buy AP rounds
The 5.56 is a well proven and established round and we KNOW what it can and does do, but much like the AR-15 that made it famous… it’s no longer the leading edge of the knife.
I’m not sure there is anything Dr. Fackler has written that I have not read at least twice.
The illustration provided there appears to be primarily comparing hydrostatic shock. From my reading of “Military Rifle Bullet Wound Patterns” by Dr. Fackler, I gathered that the hydrostatic shock is not all that reliable, and that fragmentation and the creation of multiple permanent cavities is more desirable.
While the sketches, as used by Dr. Fackler, are better at illustrating fragments than these pictures that show shredded gelatin more than anything… from what is visible here it appears that all three cartridges exhibit a similar “spread” of fragments. I’d consider 5.56mm to be superior since it does it more efficiently (the cartridge is lighter and smaller).
The past 25 years of terminal ballistics study, that I have been exposed to, leads me to the opposite conclusion.
And, before you say something, yes, I know who you are.
Not sure what you mean by saying that the AR15 is no longer the leading edge of the knife. I have yet to discover a better platform.
7.62x39mm became a poor combat cartridge when Dr. Fackler’s research indicated it has the terminal performance of a pistol cartridge… 7.62x39mm pretty much holds the title for worst intermediate rifle cartridge in widespread use today.
It sounds to me like you want a GPMG in 7.62NATO based on the criteria presented (aside from your suggestion we should get varmint projectiles to shoot people with)… why that leads you to believe 5.56NATO is not the best at its current job is illogical.
Then you’d be well served to re-examine your desire to post here. You asked, he answered, and now you are still disagreeing with him. Worse still, you are doing so in a flippant manner, which I view as disrespectful.
This is a bad idea.
It is entirely possible to carry on this conversation with a far greater deference to knowledge, obviously outside your depth, being imparted.
The great thing about the 10% gel test is that we can measure the performance of projectiles in a medium that very closely resembles the hydrolic content of human tissue. 7.62x39mm projectiles in the Hornday AMAX, or other well engineered expansion loads perform quite well in 10% gel tests. Thus, the 7.62x39 is a great cartridge when decent ammunition is used.
