Grendel as a Universal Infantry Cartridge

[stanc]

I'm just wondering about the variables we have at play: Was the jacket too thin? Lead alloy too soft? Mass just too low? (123 grains penetrated.) Block composition unusual? (It DID look different from the standard CMUs I'm used to seeing.) Velocity too low? Etc.

I'd be curious how a 90gr monolithic would do. . . .

I agree, there are a number of variables that should be looked at.

For one, the two CMUs looked to me like they were of different construction. If Chris's block was harder or had thicker walls than the block shot by Paul, that could easily account for the different penetration. Such a test needs to use CMUs from the same manufacturer.

Velocity of the Wolf FMJ was clearly too low for that lead-core bullet. I suspect that a 100gr bullet would need significantly higher velocity, even if it were to have a steel core. The air space in the tip might also have been a factor.

IMO, bullets used in testing CMU penetration should all have the same construction. That's why I suggest the Norma 120gr FMJ for comparison with 7.62 M80 Ball. Both have lead cores, with no air space in the tip. Just make sure to use gilding metal jacket M80, not the steel jacket stuff.

For testing a 6.5mm monolithic, I'd argue for a 150gr monolithic of the same make in .308 Win, in order to have an apples-vs-apples comparison.

[stanc]

I'm not sure if my calculations are right, so anyone please feel free to correct me.

If momentum density determines penetration of a CMU, to have performance comparable to a 147gr 7.62mm bullet at 2800 fps, a 100gr 6.5mm projectile would need a velocity of ~3000 fps.

[JASmith]

I'm not sure if my calculations are right, so anyone please feel free to correct me.

If momentum density determines penetration of a CMU, to have performance comparable to a 147gr 7.62mm bullet at 2800 fps, a 100gr 6.5mm projectile would need a velocity of ~3000 fps.

...or possibly as skosh faster.

Yet, we see steel replacing lead in military ammo. That will cause the bullet to behave differently on impact. The 5.56 example suggests that a "green" 100 grain 6.5 projectile might do as well as the lead core 147gr FMJ.

Fortunately, the Lehigh Defense 95 grain Controlled Chaos bullet is available and inexpensive enough to try on a variety of targets. The results could prove interesting.

[stanc]

...or possibly as skosh faster.

Thanks, Joe. Appreciated. Launching a 100gr bullet @ 3000+ fps is obviously well beyond the capability of 6.5 Grendel.

Yet, we see steel replacing lead in military ammo. That will cause the bullet to behave differently on impact. The 5.56 example suggests that a "green" 100 grain 6.5 projectile might do as well as the lead core 147gr FMJ.

I agree. Question is, what velocity would be required of a 100gr steel-core bullet? Would it still be higher than feasible with 6.5 Grendel?

Fortunately, the Lehigh Defense 95 grain Controlled Chaos bullet is available and inexpensive enough to try on a variety of targets. The results could prove interesting.

Perhaps, but I'm skeptical of the usefulness of data from brass bullet performance being applicable to steel-core projectiles.

Some time back, one of the guys on the MG&A forum shot CMUs with different calibers. In that test, a solid brass 6.5mm bullet outperformed lead-core 7.62 NATO. However, IIRC when Bill W shot a steel plate with the Barnes 110gr brass solid, it failed to punch through.

I'm especially leery of the Lehigh hollowpoint bullet in this regard, because the nose has got to be much more fragile and subject to deformation or break up than a hardened steel penetrator. I think that 7.62x39 steel-core bullets -- being in the 6.5 Grendel weight range -- would permit a better evaluation of CMU-busting ability, despite their larger diameter. Of course, the steel-core 6.5x55 112gr AP would be nearly ideal, but who knows where to get any.*

(*Maybe LRRPF52 could smuggle some back, the next time he goes to Scandinavia. )

[stanc]

It occurs to me that penetration testing is one area where John's idea of replacing the polymer tip of his ideal monolithic bullet with a long-shanked, steel tip would be a viable option.

Since this would be just for evaluating barrier defeat, it seems like it should be okay to also use lead-core bullets like the Hornady 123gr AMAX (or maybe even the Wolf 100gr FMJ?), for instance.

Photo below gives an idea of how long the shank of the metal tip should be relative to bullet length.

[stanc]

So now there are two 6.5 Grendel FMJ loads available which could be used for informal testing to compare terminal performance with that of 7.62 M80 Ball:

Prvi 110gr w/copper jacket, and Wolf 100gr w/steel jacket.

[BluntForceTrauma]

I'd like to know if the Barnaul 6.5 Grendel 100 FMJ steel-case is the Red Army War Machine's best loading. I suspect that if — in some hypothetical universe — the Russians made 6.5 Grendel their issue cartridge, that we'd see a boost beyond 2500 fps from a 16" barrel. If that's their best velocity they're either not trying very hard or they don't really understand small arms ballistics.

[stanc]

I'd like to know if the Barnaul 6.5 Grendel 100 FMJ steel-case is the Red Army War Machine's best loading.

No, John, it isn't. I don't know what muzzle velocity might be, but 6.5 Grendelski ammo would not have lead-core bullets. That's strictly for commercial sales here in the USA. Russian military ball ammo would almost certainly have a hardened steel core, similar to the 7N10.

[stanc]

To those who complained that I wasn't being fair to 6.5 Grendel when I calculated ballistics tables using the Norma 120gr FMJ (0.428 G1 BC) in comparing performance with 7.62 M80 Ball:

Using velocities from the PPU ballistics table for the 110gr FMJ ( http://www.prvipartizan.com/search_rb.php?id=A-484 ), the JBM calculator ( http://www.jbmballistics.com/cgi-bin/jbmbcv-5.1.cgi ) gives a 0.205 G7 BC (0.407 G1 BC).

That makes the BC significantly lower than that of the supposedly "poorly shaped" Norma bullet.

[BluntForceTrauma]

The standard of nicely shaped 6.5mm bullets is set by Berger's new 130 HVLD. I consider that an ideal ogive for the 6.5 Grendel which — at a nose length of 0.738 — fits exactly within the 65G's SAAMI spec nose of 0.740.

The closer any 6.5mm nose is to the Berger the closer it is to the optimum shape.

P.S. Where did you find the BC for the PPU 110 FMJ?

[acourvil]

Do you mean the 130g AR Hybrid? The VLD is kind of long.

[stanc]

Where did you find the BC for the PPU 110 FMJ?

As noted in my previous post, it was determined on the linked JBM calculator. Plugged in 0 and 300 meter velocities, and 0.205 G7/0.407 G1 is what came out.

[BluntForceTrauma]

Do you mean the 130g AR Hybrid? The VLD is kind of long.

Yes, the hybrid. I noted it as an "HVLD" (Hybrid VLD), but maybe that's not how they refer to it.

[Trooper]

Gosh, it's good to see this forum again!

Might as well start with an old Grendel topic -- how well it might serve as a universal cartridge for one or more nation's services.

I'd like to call your attention to these articles:

1. The "6.5 mm and the Politics of Procurement" at http://forums.delphiforums.com/autog...ges?msg=4491.1
2. "Grendelmania" -- series of notes at http://shootersnotes.com/grendelmania/
3. The "Battle Rifle Series" at http://shootersnotes.com/battle-rifle-cartridge/

The "6.5 mm and the Politics of Procurement" explores a replacement of both the 5.56 and 7.62 NATO rounds on a likely new platform sometime in the next 5-10 years. The discussion narrows down to a cartridge that looks like a stretched 6.8 SPC. (Be forewarned -- there were 215 posts as of the writing of this note, but the rate is slowing - likely from exhaustion!)

The Grendelmania series uses the military potential as background to focus on Grendel as a medium to large game hunting cartridge.

The "Battle-Rifle" series explores alternatives with a promising candidate that may be viewed as part of the Grendel family.

The principal difference between the Military Guns and Ammunition debate and the ShooterNotes Battle-Rifle discussion is in the assumed long range lethality requirement. One specifies that the resulting cartridge be at least as lethal as the 7.62 mm M80 round at 1100 meters. The other requires that the lethality at 600 meters be at least equivalent to the muzzle performance of 5.56 M855. Similarly, one is aggressive with assumed ballistic coefficients and the other is conservative.

I am of the opinion that the Grendel community can illuminate this debate. Let's look at these questions:

1. Is there really a need for a new military cartridge? Opinions vary widely -- and an informed discussion of what is 'good enough' may be highly useful.
2. Assuming the need exists, what platforms (AR15, AK, AR10, etc.) should the new cartridge be compatible with? The choices make a major difference in cartridge design flexibility, weight, and performance potential
3. What should be the round be capable of and at what range? Remember, this is being viewed as a cartridge capable of fulfilling the medium machine gun role!
4. What are the viable technical alternatives -- caseless ammunition, etc.?
5. etc.

The list can be a lot longer, and part of our discussion may illuminate the things that really count!

So any chance that we will ever see a 6.5mm replace the 5.56 and 7.62?

[JASmith]

Too soon to tell.

Factors against:

• The 7.62 and 5.56 both do their respective jobs very well
• The logistics tail for both is extremely well entrenched
• A soldier can carry more rounds of 5.56
• Folks think the greater power of the 7.62 gives a serious advantage over the 6.5

Factors for:

• A 6.5 with characteristics like the Grendel can satisfy all of the ruoles currently filled by the 7.62 in dismounted operations
• The 6.5 has longer range than the 5.56 with larger bullets
• A soldier can carry more 6.5 rounds than he can 7.62 rounds
• The logistics tail would be significantly streamlined with a single caliber.

The biggest issue is that it takes more than "better than" these days to introduce something new.

So, while one cannot state definitively "no chance" the likelihood is not as high as we would like.