6.8SPC vs 6.5 Grendel lethality from 3-500 meters?
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
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...
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.
Last edited by WS6; 07-29-09 at 21:47.
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.
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...
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.
Originally Posted by WS6
Won't make any difference, as the bullet's velocity will have dropped below the fragmentation threshold.
Originally Posted by crenca
IMO It's more important to look at doctrine than chase a magic bullet. At 300m and beyond US Soldiers and Marines are going to likely do one of two things; use their support weapons to pin the enemy down and close on their positions or they are going to use their support weapons to pin the enemy down and call in CAS. Head/COM shots at 300m and beyond with a 1X Aimpoint or even a 4X ACOG on a moving target are difficult if not impossible except by the most highly trained individuals. I say arm the SDMs with an M110 and have at it.
Absolutely agree! Here is a little background for my research. In Afghanistan we are getting engaged beyond the distance we train to in our marksmanship programs. Traditionally, we would fix the enemy with fire and manuever on him. Afghanistan presents several problems in that regard. First, we have too much crap to carry. Solders now have about 60lbs of gear on them, operating at elevations of 8000 feet and are slow to manuever, especially against an enemy who ussually occupies the high ground. The trend now is to fix with direct fire and call in either CAS, CCA (Apache's) or indirect fire (Normally 120mm mortars) to finish the enemy. These assets are not always available and are becoming more politically restricted, unfortunately
Originally Posted by Stephen_H
So, now we know we need to engage targets beyond 300m. Our training and doctrine don't address it and our equipment is marginally capable at that distance.
6.8 and 6.5 certainly increase lethality from 0-300m. The edge appears to go to 6.8 in the short range. However, as range increases, the edge goes to 6.5. It's better BC. means less wind drift and drop compared to 6.8, which minimizes shooter error. Its penetration capability is also better, all things equal, due to higher sectional density. Thus, my question as to the lethality at short range. If the 6.8 is substantially better I would lean more toward that round, as engagement distances in most theatres will be within 300m. If it is not, then 6.5 seems to be a more capable overall cartridge for all types of terrain.
I'm also interested in the lethality mechanism of the rounds. Since studying the 5.56 we have become fascinated with fragmentation though few military rounds of larger calibers fragment. Ideally they yaw early and create a larger permanant cavity. It seems that a longer bullet would create a larger permanent cavity when it yaws, assuming design and construction were the same.
Also, the SDM program is a joke right now. FM 3-22.9 has a total of 12 pages dedicated to the SDM. The focus is on training, which is good, but the weapons range from modified M14's and M16A2's to M4's. Optics are not standardized either. I agree, M110's for the SDM's would be great, if they fix some of the QC issues. Some balk at the cost of the system, but for the cost of one F-22 fighter we could put two M110's in each infantry squad and have a capability we have not had since the reorganization of the infantry squad in 1960 and the loss of the M1D.
Last edited by tpe187; 08-02-09 at 17:50.