How could or should the 6.5 mm Grendel be improved?

[Buck2732]

Gdsm62 Is that not reinventing the 6.5x47 Lapua. Or am I missing something?

[JASmith]

The 6.5x47 base diameter is the same as the one for the 7.62X51 NATO, so there is no gain in rounds in the magazine.

The Grendel has the same base diameter as the 7.62x39 Russian, so the Grendel enjoys about as good a magazine load out as rifles chambered for the Russian round.

[Guardsman26]

Gdsm62 Is that not reinventing the 6.5x47 Lapua. Or am I missing something?

That's a very good question.

The 6.5 mm x 47 together with the .260 Rem and 6.5 mm Creedmoor are all excellent rounds. In fact, they quite comfortably exceed 7.62 mm in a package that shoots flatter, faster and with less recoil. As JAS points out, they're the same weight and size as 7.62 mm NATO, so may not offer a sufficient increase in overall capability to justify the effort of switching.

What we would ideally like is 6.5 mm x 47 performance in a 6.5 mm x 39 package. Sadly, that dog just won't hunt. Therefore, what I'd like to see is something in between.

The 7.62 mm x 39 case is an ideal start point for an intermediate round. But if an extended 6.8 mm x 45 case were used instead, the round would have an even smaller diameter allowing more to be fitted into a standard magazine.

[JASmith]

...But if an extended 6.8 mm x 45 case were used instead, the round would have an even smaller diameter allowing more to be fitted into a standard magazine.

The 6.8x45 case is too long for the kind of bullets we would need for long range effectiveness in a 6.5 when we keep the length short enough to operate in the AR-15 class of rifles.

It would, however be very interesting when taking advantage of the length provided by the AR-10 magazine well.

That raises the question of ground rules for this new cartridge. Are we restricting to the AR-15? Are we allowing AR-10 rifles? Or, are we assuming an entirely new rifle?

I know that much of this material was covered in Tony Woilliams' MG&A forum a couple or three years ago. It seemed that the group converged on something like a modern version the 6.5mm Carcano with cartridges derived from the 25 & .30 Remington running a close second. That discussion presumed a new rifle design optimized around the cartridge.

The ground rules will make a difference in both the optimization path and the feasibility argument.

[Von Gruff]

I am reluctant to intrude in this very interesting discussion because I have no military experience and dont even have AR experience --but my 6.5 Gm with 21 in barrel easily takes the 100gn TTSX tp 0ver 2925fps, the 123 gn A Max to 2700 and the 129gn Interlock to 2550 in Lapua fireformed 7.62x39 brass. About all I would like to see with this brass is a little better neck length as when FF I get a case length of 1.5 so another .02-.03 would be good. COAL with the TTSX is 2.380, with the A Max at 2.405 and the Interlock is at 2.320 and I know Sneaky One has his AR magazines except over 2.3 so somewhere there has to be a combination of these paremeters (with adjustments of throating and COAL) that might come within the requirments you are all talking about.

[stanc]

The 7.62 mm x 39 case is an ideal start point for an intermediate round. But if an extended 6.8 mm x 45 case were used instead, the round would have an even smaller diameter allowing more to be fitted into a standard magazine.

According to my calculations, if we're talking about a 25-rd magazine, the difference in capacities would be no more than one round, at most, and maybe zero rounds. That doesn't seem significant to me.

[LRRPF52]

I am reluctant to intrude in this very interesting discussion because I have no military experience and dont even have AR experience --but my 6.5 Gm with 21 in barrel easily takes the 100gn TTSX tp 0ver 2925fps, the 123 gn A Max to 2700 and the 129gn Interlock to 2550 in Lapua fireformed 7.62x39 brass. About all I would like to see with this brass is a little better neck length as when FF I get a case length of 1.5 so another .02-.03 would be good. COAL with the TTSX is 2.380, with the A Max at 2.405 and the Interlock is at 2.320 and I know Sneaky One has his AR magazines except over 2.3 so somewhere there has to be a combination of these paremeters (with adjustments of throating and COAL) that might come within the requirments you are all talking about.

Your real-world results with a Grendel chambered in a bolt gun are what I've been trying to tell some of the new members to the discussion about increasing the velocity of the Grendel. The only real thing you need to push the case to what it will handle is a stronger bolt. You could extend the COL a tiny bit, but I don't think it's necessary.

You will not get 6.5x47 Lapua performance from a shorter cartridge with a smaller diameter base, and an assault rifle or machinegun should never be run at 6.5x47 Lapua pressures in that bore diameter.

When we start talking about going back to a battle rifle-sized weapon, we have failed the soldier, the mission, and the logistics chain. You want to know what to do to improve the 6.5 Grendel?

Shoot thousands of rounds through it. Any increase in powder capacity will not be able to be exploited by well over 95% of Infantry Soldiers, and the few that can will not see a practical difference at distance anyway.

[JASmith]

What are the constraints?

My experience with previous discussion on this topic as well as in actual weapons concept definition suggests that we need to establish ground rules for comparisons. In this regard, I'm not clear on what the "new" cartridge is expected to do.

1. Match the 7.62X51 at 1000 meters?
2. Same barrel length, or a 16" 'new' and a 20" 7.62x51?
3. What does 'match' mean?

For example, if you want lethality to be the same, does that include probability of hit with one shot, or with a magazine load?

I know that this series of questions appears to move in the direction of complexity, but the restraints are needed. The alternative is akin to wrestling a bunch of pythons all at once. We can spend tens of posts on one item of performance with only to find that the OP had a different metric in mind than poster B, and Mr C has an entirely different one. This leads to confusion, frustration, untoward comments, and no convergence on a common solution.

If we are talking about wounding potential, we know that kinetic energy is one of the poorest metrics one can choose. This begs the question of what metric to use.

[adrenaline junkie]

I think a "Super G" defeats the purpose. There's already the 6.5 Creedmore and the 260 Rem which would be an even easier swap because it's based of the 7.62x51, and would already have more power than a slightly lengthened Grendel.

[stanc]

I think a "Super G" defeats the purpose. There's already the 6.5 Creedmore and the 260 Rem which would be an even easier swap because it's based of the 7.62x51, and would already have more power than a slightly lengthened Grendel.

Easier, yes, but also more powerful than deemed necessary, as well as heavier and bulkier than acceptable.

The goal is a cartridge that achieves the desired performance, without excessive weight and bulk. A "Super G" would accomplish that end; 6.5 Creedmoor and .260 Remington would not.

[ricsmall]

Anyone thought about the concept of Olympic arms UMAR lower? It's a standard ar15 lower with the mag well machined out for a larger magazine. It works for the 22-250, I don't know about combat feasibility, but it works for civvies. I've pondered it for my extremely long throated Grendel. Just a thought.

[adrenaline junkie]

A super g thats 10-15% longer is only a couple mm shorter than the other two, in a weapon that is much larger. (Ar10 vs ar15) I dont think a new cartridge would be any benefit. A weakened 260/6.5cm in the same gun is losing power at the same weight.

[LRRPF52]

All that is needed for more performance is a stronger bolt/barrel extension. The case will handle 62,000psi already, but do you really need or want to run weapons at 62,000psi in high volume? To get 100-200fps more mv, is it really worth it? What does 200fps mv give you over current mv, before a military powder has even been developed and tested under the current constraints?

[stanc]

A super g thats 10-15% longer is only a couple mm shorter than the other two, in a weapon that is much larger. (Ar10 vs ar15)

Ideally, it would be "AR12.5" vs AR15. Somewhat larger, certainly, but not as much weight and size penalty as AR10 vs AR15.

[KentuckyBuddha]

Grendel is the norse monster that goldilocks chose just the way it is!

I chuckled at AR 12.5, I may steal this as my own...sorry.