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This is some awesome data! Thanks for providing it!
Here is some more, I repost this data somewhat frequently because it's completely trounces the anecdotal comparisons that are typical of caliber arguments. It's kind of like the engine analogy when people argue engines....there's simply no replacement for displacement and that has proven time and again at the track regardless of technical arguments for or against. In the end, you just have to use it and see how it pans out.

Keep in mind I don't generally agree with the mindset that "well if the AR platform allowed a longer case like 6.8x47mm" yada yada yada it would be x amount better but we'll have to settle for it as is....those arguments that talk about further increasing velocity via a larger case are moving too close to a full powered cartridge like 7.62x51...at some point it just becomes a slightly underpowered .308 with all of the draw backs of a full powered cartridge....why not just use .308 then?

Keeping muzzle energy in the 1600 to 1800 ft-lbs (depending on load, SAAMI spec, Handloads or NATO equivalent) range for 110 to 120gr keeps the ammunition weight low, capacity high and recoil low all of which are endearing qualities of the original 5.56 cartridge we don't want to move too far away from, while simultaneously addressing it's weaknesses.

However unlike 5.56, 6.8 SPC offers significantly increased single shot terminal performance and intermediate barrier penetration which are the weaknesses of 5.56, a somewhat marginal performer for medium sized game and human enemy combatants. 5.56 is lethal, but does not provide optimal incapacitation in a a variety of situations because well....there is just no replacement for displacement!

Weather by happenstance or not, keeping it to a small frame AR platform has basically created a modern American take on the 7.62x39mm concept. Unlike 7.62x39mm however, 6.8 SPC provides decent mid-range performance where 7.62x39mm tends to really start to peter out past 300 yards and is more optimal at close range, but is quite devastating at close range with modern fragmentation or expanding loads, ask hog hunters running that cartridge. It's more or less a 54R Short, kind of like 6.8 SPC is akin to a .270 Short.

Even the SAAMI spec commercial loadings offer good performance relatively, typically in the low to mid 1600 ft-lbs muzzle energy range out of a 16" barrel which is right on par with 7.62x39mm for close range applications while basically matching the trajectory of 5.56 77gr IMI Razor Core when also fired from a 16" barrel. I chronoed IMI 77gr Razor Core 5.56 in my 16" Daniels barreled 5.56 upper at 2586 fps average on the same day I chronoed 110gr Hornady OTM in my 16" Daniels barreled 6.8 upper...so it is what it is and that's what it's producing the real world (5.56 is particularly sensitive to barrel length, especially with heavy loads).

With 110gr Hornady OTM factory (aka American Gunner line, now discontinued, but using the original 110gr OTM bullet), I get 2584 fps average. Both Daniels Defense barrels are chrome lined, hammer forged, mid-length. Same chrono, same day one hour apart on the same lower. The 5.56 barrel is 1:7 twist 6R, the 6.8 barrel is 1:11 5R. Both even run the same muzzle device, an AFAB on the 5.56 upper and EFAB (7.62 version) on the 6.8 upper. Note the efab has slightly better flash suppression due to divergent nozzles, but from a back pressure standpoint, identical, similar design overall.

Both loads (77gr Razor Core and 110gr OTM) are MOA or just below MOA (I only have 6x mag LVPO, so better magnification I could probably squeeze a bit more out of both like a 15x Nightforce for example). Run of the mill 110gr 6.8 loads only running SAAMI spec pressure offer significant overmatch to even the best 5.56 loads without question. At close range, they are in two different leagues and barrier blind performance (for any tactical applications), is vastly superior with 6.8 as well.

The only thing I'd change about 6.8 is wanting factory NATO spec loadings (higher chamber pressures) to maximize performance a little more, but even as is, it's still quite superior, more is NOT always better in practice either, more muzzle energy = more recoil = slower follow up shot split times. For hunting or long range use, hot loads may be more beneficial, but for general purpose, I think SAAMI spec is quite optimal and extends component life. There is ALWAYS a trade off, so the question becomes what is the best balance for the application?
 

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On a side note, if you go to page 12 of the Zhou19394 document, the table of parameters describing real world terminal performance note that the distance from the point of impact to the peak of the temporary cavity stretch should be between 4 to 6 inches.

Scrolling back up to the data from brass fetcher, lo and behold, 6.8 produces peak temporary cavity stretch at or just a tad past 4 inches in all three tests, direct impact, through auto glass and through a car door. Again, real world data comparing the same bullet design in three different calibers and 6.8 out performed the other two.

Brass Fetcher focuses mostly on LE and Federal agencies, not so much on military applications. However it's another independent source that corroborates the findings of the ballistics research used to test and develop the 6.8 SPC cartridge back when the US military was developing 6.8 SPC.

I'm not suggesting 6.5 caliber projectiles are always inferior, however they don't offer much added terminal performance over 5.56 caliber projectiles of the same bullet composition and design, but do extend the range at which they can be used effectively over 5.56 caliber projectiles due to better exterior ballistics.

6.8 caliber projectiles (and larger caliber projectiles if a larger case is used) accomplish both an increase in terminal performance and the maximum range at which ideal terminal performance occurs with the added characteristic of good barrier blind performance which is very important for any sort of tactical application, Military, LE or even some home defense scenarios depending on location / surroundings. However the trade off then becomes at some point added weight (both ammunition and the platform, such as an AR-10 vs AR-15), recoil and reduced capacity. We then circle back to how much is too much vs. what is just right for the application?

And no, none of this matters if you miss the target or hit a non-critical area like someone's pinky finger or a deer's tail....fundamentals of markmanship always apply, however terminal performance is an important 3rd characteristic and size does matter in this case ;-).
 

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What powder do you use to get 2750 at the muzzle from a 16" barrel? With 28.9grn of 2200, 1:11 ,4 grove BBL I was getting 2609. temp. was 48F. @ 4270 ft elevation
It very well could be your barrel , ARP barrels produce 50-100 FPS more velocity than any other barrel out there. Not being a smart [email protected]* or knocking your barrel just stating the facts.
 
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