Quoted: The guys behind the SPC tried a 6.5, but decided against it. I don't know why.

I've posted the reason why at least two dozen times...

Many folks who were on the SPC development team *assumed* that the 6.5mm bullet was going to be the winner.  Everyone certainly liked the accuracy and trajectory that the 6.5's are known for, and there was actually a bias towards 6.5mm when it started.  But the 6.5 bullets simply did not meet the performance requirements.  Specifically, the 6.5 bullets penetrate way too far before they begin to yaw and fragment.  Depending on the bullet, the "neck" of the wound will be anywhere between 4-8".  That's WAY outside of the desired profile.

The testing showed that the 6.8mm was very good, and that the 7mm was a bit better in terminal ballistics, but that the 7mm's trajectory was somewhat poor, it was less accurate, and had a shorter fragmentation radius due to the lower initial velocity compared to the 6.8mm.  Thus, 6.8mm turned out to be the "sweet spot".  Had the AR been designed around a longer cartridge (say, halfway between 5.56 and .308), the 7mm would have occupied the sweet spot (good enough infact to REALLY replace both 5.56 and .308), but cases small enough to fit into a 5.56 weapon simply don't have enough case capacity to make the 7mm work well enough.

The 6.5 cartridges, such as the Grendel, are still fantastic match rounds, and will work well for hunting applications that require more penetration than the "combat vs humans" profile, but they simply don't work well as a combat bullet.  And while I won't say that making a 6.5mm bullet that gives the required profile isn't possible, I *can* say with a fair amount of confidence that it isn't practical.  The already thin bullet jackets would have to be made even thinner, yet maintain a higher degree of consistancy, and still be tough enough not to be shredded by the rifling.  I think most people understand that manufacturing costs rise *significantly* as the required level of precision is increased, and that *assumes* that thinner jackets would still be tough enough, which may not be the case.

Certainly, you could design or use a bullet that is *designed* to fragment, such as a V-Max, but such a bullet wouldn't be JAG-legal, and would then not have a military application.

The 6.8mm SPC has been shown to be 1 MOA accurate at 600m from a 12" barrel at the US Army's fully-instrumented Parks shooting range, so it has plenty of accuracy to do the job.  Certainly no one can honestly suggest that an AR should be relied upon to make "stops" on point targets beyond 600m, as NO bullet available for the AR platform has enough energy left at 600m to incapacitate reliably with a torso shot.  That's really .308 or larger territory in the first place.

The great thing about 6.8 SPC is that it does all of the jobs that the AR platform is realistically required to perform, from CQB with very short weapons to "Designated Marksman" roles out to 600m, and it does them all very well.  No other cartridge that currently exists does THOSE things better.

-Troy

Quoted: Quoted: The guys behind the SPC tried a 6.5, but decided against it. I don't know why. I've posted the reason why at least two dozen times...

It's getting old, isn't it?  Maybe you should set a macro function on your keyboard to automatically post your response

Quoted: Quoted: Certainly, you could design or use a bullet that is *designed* to fragment, such as a V-Max, but such a bullet wouldn't be JAG-legal, and would then not have a military application. I thought that's what the 6.8 SPC gelatin tests were done with, a VMAX without the polymer tip?   If that's not the case, then what bullet did they use?

115gr OTM, which *is* JAG legal.

Gel tests have also been done with the 110Vmax as well, of course, along with the 115gr FMJ.

Quoted: In the Grendel, the higher BC is mostly because it can use longer bullets.  You'll lose that advantage if you use the 6.8 SPC case.

Correct

IMO, the other way around would be more interesting.  Use a 6.5 Grendel case with the 6.8 magic bullet.   That way, you'd be able to use high BC bullets long range, and still be able to use the magic bullet for CQB.

Once again, you'd have case capacity problems, as heavier bullets need slower powder, and you wouldn't have enough for an optimal load, so your velocity would be low, negating any BC advantage.  Plus, you'd have further lowered mag capacity, and the over-all length of the round would be too short with the standard 6.8 bullets.

This is yet another example of how all the components of a gun and its ammo work together as a SYSTEM.  Many times, it isn't possible or practical to change a component of that system without making significant changes to other components in order to keep things working.

-Troy

Quoted: Energy itself doesn't do crap to incapacitate. It's what the bullet actually does. At 600 yds a .223 bullet won't fragment/expand, and most likely won't even yaw. You'll have a .22 inch wound all the way through.

It actually will yaw, but only after a LOT of penetration, so that isn't going to do a whole lot of good.  It certainly will be very poor in comparison to a 45 ACP, which uses bullets that are designed to work at low velocity/energy levels.

Pistol bullets and rifle bullets work very differently, and what is true for one is not going to be true of the other.  This is one of MANY reasons why using energy figures to compare different bullets and ESPECIALLY different calibers a bad idea.  The amount of energy a bullet has at a given distance only tells you how it is likely to work, given that bullet's design and construction, and is useful mostly for comparing the bullet's performance against itself over distance.  It is a poor tool for comparing performance against dissimilar bullets.

-Troy

Quoted: Quoted: Quoted: Certainly, you could design or use a bullet that is *designed* to fragment, such as a V-Max, but such a bullet wouldn't be JAG-legal, and would then not have a military application. I thought that's what the 6.8 SPC gelatin tests were done with, a VMAX without the polymer tip?   If that's not the case, then what bullet did they use? 115gr OTM, which *is* JAG legal. Gel tests have also been done with the 110Vmax as well, of course, along with the 115gr FMJ.

It was originally done with the 110gr OTM, which was available off-the-shelf, as the development team had no money or support (initially) to develop a new bullet.  It worked very well, but along the way, a couple of the big ammo companies lent their support to the project, and developed some 115gr bullets to further optimize the cartridge, which is how we got the 115gr OTM and FMJ bullets.  The excellent (but not JAG-legal) 110gr VMax is an off-the-shelf bullet, of course.

-Troy

Quoted: For years I'd thought that when the US went from the 7.62X51mm to the 5.56X45 that they had gone too far.

Really, they did go too far.  But politics, budget issues, and lack of any real scientific understanding of terminal ballistics, the limited testing that was done showed that the round (M193) did pretty well (from a 20" M16).  That combo would still work as well today, but that's NOT the rifle the military wants to carry today.  They want ever-shorter barrels, and short barrels kill the 5.56's performance.  It's just taken FAR to long for the military to admit and acknowledge that fact, and they still have not fully done so, in order to prevent a loss of confidence by the troops who are still issued those weapons.

-Troy

Quoted: once again, troy, i would like to thank you for crushing my hopes and dreams.

Sorry, man, but that was REALITY doing all the crushing.  I'm just the messenger.  

-Troy

The glacier-like pace of Remington getting ammo out to the civilian world HAS certainly been the biggest obsticle for the 6.8mm, but it looks like a couple of additional players will be entering the market shortly, and THAT is really going to be when 6.8mm will start to get interesting.  There are bound to be some unexpected problems, and probably some interesting developments as well, as the cartridge sees mass production and has to work in guns of various manufacture and assembly, but in the end, we should really have a great round.

-Troy

The bullets used in the 6.5 SPC testing could easily be loaded in the Grendel case.  You would probably get a bit more velocity from them in the Grendel case, but not a significant amount, as case volume between the two is quite close.  Regardless, the terminal ballistics wouldn't change; the 6.5mm bullets ALL seem to penetrate much too far before beginning to yaw.  Again, there are known designs that would make that irrelevant due to their wounding mechanism (softpoints), but these aren't JAG-legal, so that's a moot point when it comes to military adoption.

-Troy

Quoted: Quoted: The glacier-like pace of Remington getting ammo out to the civilian world HAS certainly been the biggest obsticle for the 6.8mm, but it looks like a couple of additional players will be entering the market shortly, A very wise man recently recommended I write to Federal and Black Hills to suggest they start loading the 6.8SPC. I would like to suggest we ALL write letters or e-mails.

I have spoken to Jeff Hoffman (Black Hills) about this.

It's not possible until brass is readily available.  Otherwise, he tod me that he is interested in making 6.8.