6.5 Grendel vs 6.8 spc reliabilty???


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Float Pilot
October 5, 2008, 09:48 PM
For those of you who have fired both the 6.5mm Grendel and the 6.8mm SPC extensively....

Is there really a reliablity difference between the two cartridges when fired from an AR platform?

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Marcus L.
October 6, 2008, 06:27 AM
It's doubtful that you'll find someone who owns both, let alone someone who shoots both enough to give you an accurate determination of feeding reliability. You're also unlikely to find an individual who does not have some bias that will skew any information that they give you one the subject matter. A lot of AR shooters that use non 5.56 calibers don't push their platforms beyond bench shooting with optics anyhow. This is why we look to weapons testing by large military or police organizations which have reduced bias and really put equipment through a beating. The 6.8 SPC has undergone extensive JSWB-IPT testing, FBI BRF testing, USMC testing, and the recent CTTSO/TSWG MURG Congressional demonstration. Every aspect of its development was done in increments to determine the ideal caliber, ideal case capacity, ideal case characteristics, and ideal terminal performance.
http://www.dtic.mil/ndia/2008Intl/Roberts.pdf

The Grendel on the other hand was designed from scratch to fire a 6.5mm projectile at a target velocity of 2200fps-2400fps at the muzzle with little if any considerations for important factors as I mentioned in the previous sentence.

There is also another option which is gaining ground as a universal military cartridge replacement. Given no platform restrictions(M4/M16), the same guys who designed the 6.8 SPC also designed the 7x46mm which lauchest a 130gr bullet at around 2600fps from a 16" barrel. This round was considered to be the ideal universal cartridge in that it is controllable from a short full auto carbine, but is powerful enough to be used in medium machine guns and sniper rifles. Basically, a return to the standardization logistics of WWI and WWII where the .30-06 was the universal cartridge.

everallm
October 6, 2008, 09:08 AM
As mentioned above relatively few folks go down both routes.

Hopefully though you should be able to get some real world stats in a couple of months when Robinson Arms get the 6.5 barrels and conversion kits for the XCR rifle out the door.

There are a number of folks with the XCR in 6.8 who already have the 6.5 on order and will be able to do direct side by side comparisons with the 2 calibres on the same rifle.

It will be very interesting to see actual real world comparisons, like for like.

Float Pilot
October 6, 2008, 03:12 PM
large military or police organizations which have reduced bias

From 1977 until 2006 my career was centered around both those with a lot of overlap.
We just hid ur bias with BS or were ordered to promote the bias of those from whom we took our marching orders.

Marcus L.
October 6, 2008, 05:24 PM
From 1977 until 2006 my career was centered around both those with a lot of overlap.
We just hid ur bias with BS or were ordered to promote the bias of those from whom we took our marching orders.

I hear ya, I've seen the bias myself in the military and now in the Federal police system. However, they are the only two organizations that get a large number of testers together, buy a large number of firearms to test, and buy thousands-to-millions of rounds and put it all through rigorous paces. The Department of Homeland Security went through over 3-million rounds of .40S&W and almost 300 pistols before they adopted the Sig P229.

Rumor has it that the Grendel has been seeing a lot of testing in addition to the 6.8 SPC with the agencies I listed in my first post. Right now, the 6.8 SPC is in the lead. I don't know what the problems are they are finding with the Grendel, but they are likely due to several issues that I have posted about before. Lack of good terminal effects with many different bullet designs, steep case shoulder which reduces feeding reliability(short magnum syndrome), and short case length which makes it a poor choice for belt fed weapons(short magnum syndrome again).

The last post I made on this thread has some good visuals of the terminal effects problems:
http://www.thehighroad.org/showthread.php?t=396783&page=2

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