6.8SPC vs 6.5 Grendel lethality from 3-500 meters?

[tpe187]

The military application of these two cartridges is very interesting. The renewed focus on operations in Afghanistan has hightened that awareness that about 50% of the engagements are occuring over 300 meters. This is outside the effectiveness of M855 or MK262.

I've been able to find significant information about the lethality of the 6.8 SPC, specifically in its 110/115 Hornady OTM applications, but not nearly as much on the 6.5 Grendel.

In summary, the 6.8 reliably fragments down to about 2100fps, giving it a fragmentation range of about 250 meters out of a 14.5" carbine. This is vastly superior to current issue M855 with a fragmentation range of about 150 meters out of a 14.5" carbine, 70% of the time.

6.5 Grendel has a better BC. for its rounds, specifically using the Lapua 123gr bullet. I don't know what the velocity threshold is for its reliable fragmentation, but assuming a similar 2100fps, it would seem to extend the fragmentation range to about 400 meters. We need a caliber that extends the range of the infantryman to about 500 meters. My initial research suggests that 6.8 SPC is a likely canidate based on its development and testing. Now that I've been looking into the 6.5 Grendel, it seems its retained velocity at distance makes it a better canidate for Afghanistan.

Caveats: I understand that shot placement is more important than caliber or bullet performance and that fragmentation is not the only lethality mechanism of these two rounds.

So, all that out of the way, what testing has been done on 6.5 compared to 6.8? I don't have a copy of the JSWB-IPT that Doc Roberts cites in his many posts, but I imagine they would have tested it extensively.

Is 6.5 a better cartridge than 6.8 at distances from 3-500 meters?
Inside of 300 meters is the 6.8 SPC markedly better than 6.5?
Outside of fragementation range, is the permanent wound cavity significant enough to reliably incapacitate?

Hopefully some of you with more experience than I can chime in and help me out. I'm sure Doc Roberts will share his findings as well. Thanks

[crenca]

The 3-500 meter distance is that point at which the 6.5 "catches up" with the 6.8. I would think just where in that distance this happens would really vary from loading to loading. Nothing to back this up, just my impression from reading up on the 6.5 (I am a 6.8 shooter).

As to bullet frag and terminal ballistics of 6.5, I would be interested in a good side by side ballistic get test also. Not sure one has been done however. 6.8 seems to have the edge in bullet selection right now so again, it would depend on the loading...

[WS6]

Almost 50 years ago we got rid of a piston driven platform in a NATO standard caliber capable of anchoring a man at 800m if you conntected. 20 years ago, we got rid of an effective handgun round that generated little, if criticism from the field relating to it's effectiveness.

I am amused to see both making a come-back. It seems clothing isn't the only revolving fashion.

[Zhukov]

Isn't 300 yards about the max fragmentation range for these calibers? Once you move outside of fragmentation range, I would expect the differences to be minimal, as they're both non-fragmenting projectiles of approximately the same diameter. I'm sure DocGKR will have a better answer though.

[crenca]

I was wondering whether the better sectional density and velocity of the 6.5 would not make it a better terminal ballistic wise after about 3-400. No doubt some gel testing would show either way...

[Zhukov]

I was wondering whether the better sectional density and velocity of the 6.5 would not make it a better terminal ballistic wise after about 3-400. No doubt some gel testing would show either way...

Won't make any difference, as the bullet's velocity will have dropped below the fragmentation threshold.

[stony275]

Almost 50 years ago we got rid of a piston driven platform in a NATO standard caliber capable of anchoring a man at 800m if you conntected. 20 years ago, we got rid of an effective handgun round that generated little, if criticism from the field relating to it's effectiveness.

I am amused to see both making a come-back. It seems clothing isn't the only revolving fashion.

Look at post WWII and the British EM2 in .280 caliber. If I'm not mistaken, the FAL was originally designed around that caliber as well. We could have saved ourselves a lot of trouble if we had adopted that cartridge from the get go.