How could or should the 6.5 mm Grendel be improved?

[stanc]

a. Or is it better to have a caliber that only moderately improves effective range in one theater in the hands of the few who will actually be able to employ it (10% of the Army/Marines)...

How do you know that it would only moderately improve effective range? I've yet to learn of any testing that demonstrates to what degree hit probability would change with either 6.5 Grendel or the notional 6.5 GPC.

...while reducing combat endurance for them across the board in all theaters, and saddling all the soft skills with the same issues of increased recoil, reduced ammunition capacity per weight?

Is it likely to make any noticeable difference on combat performance of the soft skills? Do they currently make a significant percentage of a unit's kills?

Would the reduced machine gun ammo weight and increased mobility for gunners balance out the combat endurance?

You can probably answer that better than I. What is the current ratio of enemy casualties inflicted by machine gunners versus riflemen?

c. With the 7.62 NATO system, SMG's and older era carbines were predominant in the hands of key leaders and non riflemen personnel, not only in the US, but in the European nations and their former colonies. The Bundeswehr with the Uzi and MP5, the Italians with the Beretta SMG, the Sten with the UK, the M1 Carbine with the US (Army Special Forces held onto the M1 and M2 Carbines up until they received the AR15, and the 82nd + Airmobile units couldn't ditch the M14 fast enough.)

I can't speak to the Europeans, but I seriously question that US key leaders and RTOs carried SMGs or M1/M2 carbines in the late-1950s/early-1960s. Special Forces, yes, but not line infantry.

On top of that, the M14/M60 universal caliber system was a terrible failure operationally in Vietnam, due to limited combat endurance and a drag on the logistics system to re-supply units constantly after very limited contact.

I won't dispute that, but remember, those 7.62x51 weapons and ammo were significantly heavier than 6.5 Grendel and 6.5 GPC, which would therefore be less limiting in those respects.

In that light, we might even consider getting rid of 5.56 NATO and 7.62 NATO and do a PDW based off the 6x.221 Fireball for riflemen (KAC 6x35 PDW), the high-powered Grendel for DM's and LMG's, and some .338 Long-Range weapons to replace the .50 BMG. You can carry a ton of rounds with the 6x35, since the cartridges are shorter, while not losing a lot of effective range for practical engagement distances.

Imagine the endurance of a unit that has riflemen/assaulters with 300rd basic loads, with Multi-Role LMG gunners able to carry more than a 7.62 GPMG in less space/weight, with DM's and Snipers carrying lighter, more wind-bucking, less-recoiling blasters, with the Grendel and .338 LM systems, ditching 7.62 NATO, .300 Win Mag, and .50 BMG.

An intriguing idea, and worth investigating. Needs testing, though.

When the discussion encompasses all the systems we really carry, anyone realizes straight away that any illusions of a universal caliber are quite narrow in scope.

Obviously not everyone realizes that, or discussions like this wouldn't be taking place.

The thing is, no army in the post-WWII era has tried the envisioned GPC concept, so there's virtually no evidence to judge if it is a good or bad idea.

[stanc]

...outside the wire in a combat arena, I want general purpose rifle (GPR). The problem is that as a GPR, the M4 (5.56x45) is too light and the M14/M110 (7.62x51) is too heavy. A GPR using a 6.5mm round makes more sense.

In theory, I agree. But, I'd sure like to see some comparison testing done to find out if theory translates to reality. Say, perhaps have a number of shooters with varied skill levels, run through different scenarios alternately with a 5.56 M4, a 6.5 Tac 14.5, and a 6.5 Tac 16.

[LRRPF52]

In theory, I agree. But, I'd sure like to see some comparison testing done to find out if theory translates to reality. Say, perhaps have a number of shooters with varied skill levels, run through different scenarios alternately with a 5.56 M4, a 6.5 Tac 14.5, and a 6.5 Tac 16.

I've done this with my BIL to a degree. The first time shooting my 16" Grendel, he cleaned my poppers at 300m, went to 400m and hit everything 1st-round, then made a 1st-round hit at 500m on a steel IPSC target, with the impact dead center for windage.

He used the drop chart I had generated for it with Brian Litz's Berger Ballistics program, and me on the spotting scope giving him his wind calls, since we literally had a 20mph full value wind. Without my wind calls, he wouldn't have made 1st-round hits.

The main factor missing is training and experience, although a 6.5 Grendel will allow entry-level soldiers to miss closer than they would with a 5.56 NATO carbine, and close misses translate to more effective fire on the enemy to a degree. What really needs to change is the rifle marksmanship programs for professional armies, even if it only means running an intermediate rifle marksmanship course for combat arms personnel before they deploy.

Such a course would involve a lot of time dedicated to teaching external ballistics, use of optics, wind-reading, and range time putting rounds out from 100-600m+ with increased 1st-round hit probability. Only a free-floated system with consistently accurate ammo will really do that, like the SPR, DMR, M4A1 SOPMOD Block II, etc. using 77gr Mk.262 for the 5.56 NATO guns. We're basically talking about a Designated Marksmen course, which would be very difficult to run for every Rifleman in an Infantry battalion, let alone Brigade. It's just not feasible really for everyone, when you look at the range usage, ammunition, instructor experience pool, and weapon requirements.

It is a viable program with 1 out of 4 screened, selected, and trained for a minimum 5-day DM course, and many units have been doing something along these lines, as the DM is now a TO&E position in the US and many coalition nation armies, but still in the growing stages.

[stanc]

I've done this with my BIL to a degree. The first time shooting my 16" Grendel, he cleaned my poppers at 300m, went to 400m and hit everything 1st-round, then made a 1st-round hit at 500m on a steel IPSC target, with the impact dead center for windage.

He used the drop chart I had generated for it with Brian Litz's Berger Ballistics program, and me on the spotting scope giving him his wind calls...

I'm not sure how much value to place on your BIL story. It appears to me that riflemen don't use drop charts, let alone have spotters with high-power scopes.

...a 6.5 Grendel will allow entry-level soldiers to miss closer than they would with a 5.56 NATO carbine...

Where is the test data to support this claim? The "I'm hit!" video I posted shows what seems typical for how soldiers shoot in combat. Judging by that, I cannot see how they would likely "miss closer" with 6.5mm than with 5.56mm.

[LRRPF52]

It appears to me that riflemen don't use drop charts, let alone have spotters with high-power scopes.

Exactly the point. In cases where riflemen have decent positions behind some type of cover, and are able to make well-aimed shots at enemy combatants where wind begins to be a significant factor, they will miss closer without any training in wind-reading and compensation. If they are able to see where their misses register, keeping in mind that enemy fire may be flying past their faces and impacting nearby, you could make the argument that a cartridge with less wind deflection would be of some benefit, but under combat conditions of 2-way gun-fighting, trying to see your hits is not exactly like it is on a 1-way range.

The "I'm hit!" video is actually atypical, especially when you dig into the back story. The soldier who filmed it with his helmet cam, was an LEO before joining the Army at an unusually old age, 38 IIRC. By his own account, he was attempting to draw fire away from his squad:

"I was heading down the face of the hill when we got hit. The rest of the squad was pinned down by machine gun fire. I didn’t start the video until a few minutes into the firefight for obvious reasons. I came out into the open to draw fire so my squad could get to safety. I was hit in the side of my helmet and my eye [protection] was shot off of my face.”

That's not exactly a battle drill that is taught or sanctioned, especially since he seems to have gone lower than them on the mountain, making it even more difficult for the unit to withdraw, as we never leave a fallen comrade to fall into the hands of the enemy. You are correct that indiscriminate fire is ineffective, regardless of caliber, but the "I'm hit!" video is a lesson more in tactics than anything. If one of his comrades with DM training was able to get into a good position without being seen, then place effective fire on the PKM that was lighting the "bait" up, this might have been successful.

[stanc]

Exactly the point. In cases where riflemen have decent positions behind some type of cover, and are able to make well-aimed shots at enemy combatants where wind begins to be a significant factor, they will miss closer without any training in wind-reading and compensation.

Ah, okay. I'll buy that.

The "I'm hit!" video is actually atypical...

I have to question that. The manner in which he was shooting looks the same as I've seen in countless other videos of Afghan firefights. For instance:

https://www.youtube.com/watch?v=QvsQriCvyx8

[Tony Williams]

You can change the controllability of an assault rifle on AUTO if someone would actually make an assault rifle using the operating principle of the original grandaddy of all assault rifles, constant recoil combined with a low cyclic rate of fire, which is the most over-looked set of features of the Sturmgewehr Stg44.

The benefits of a constant-recoil operating system combined with low cyclic rate are more apparent on AUTO than SEMI, and favor AUTO because you don't have as rapid follow-ups in the SEMI mode due to slower bolt carrier velocity. This is where the AR15 shines, because you can hose away with it on SEMI and run extremely fast follow-ups. The Stg44 didn't need a SEMI mode really, because you could touch off 2rd bursts without any real muzzle climb or significant recoil. It's a design that remains ahead of its time.

If you really want a great assault rifle that goes where none have gone before all in one, you use a lengthened receiver where the bolt carrier never impacts the rear like a j(AK) hammer,

I think that's an important point which is almost always ignored by western gun designers. I've seen the recoil impact chart for the M4 and that shows two peaks: the first when the bullet and propellant gas are accelerated out of the muzzle, the second (slightly higher) when the bolt hits the buffers.

The STK Ultimax 100 SAW has the very long recoil stroke you are asking for and, although I've never fired one, I gather that they are very controllable on auto. The resulting lower rate of fire makes its own contribution to manageability, of course (as well as slowing barrel heating and ammo consumption).

Even more promising is the Russian balanced-piston design as introduced in the AEK-971 in the 1980s and now used in the AK107. There's no reason why a balanced piston couldn't be combined with a long recoil stroke - that should take auto controllability to a new level. Probably wasted on such light-recoiling rounds as the 5.45mm and 5.56mm, though.

[LRRPF52]

The problem with the AK-107 is more moving parts and a cog wheel that drives the counter-reciprocating piston forward. It's basically a demonstrator model that will never be fielded.

[Tony Williams]

Yes, there are more moving parts, but the key question is whether the system can be made to work reliably under combat conditions. That can depend more on the fine detail of the design than on the major operating system.

[Guardsman26]

Sorta like this?

www.youtube.com/watch?v=rLHU-_OhT8g

Stan,

Yes. Absolutely. The point this film makes is not that 5.56 mm can't hit at longer ranges, but that it can't even suppress. When our friends Hall and Hitchman proposed SCHV because combat ranges seldom exceeded 300 metres, they completely forgot to think about suppression. Just having lots of rounds to fire in the general direction of the enemy isn't suppression. Suppression, as anyone with military experience here will know, is making the enemy keep his head down.

UK analysis of combat engagements post WW2 by the Ideal Calibre Panel similarly concluded that the killing is mostly done at ranges of less than 300 metres both in attack and defence, but that it also looked at suppression and concluded that this can take place at ranges out to at least 1,000 metres. If you think about a simple platoon or company attack, you have one section / squad that lays down covering (suppressive) fire while the two other squads manoeuvre into an assault position. If the Platoon Leader is any good, then hopefully the final assault will not be over more than 50 metres. But frequently the fire support team will be laying down fire at ranges above 600 metres.

Would a 6.5 mm Grendel have made a difference? Absolutely. An 8 gram bullet has a much larger sound signature as well as the ability to reach out to 1,000 metres. In a machine gun that could have been very useful in the situation described in the video.

You're carrying 25 rounds instead of 30 in a weapon that weighs more or less the same. What's not to like? In short, the Grendel isn't perfect, but it's a such a superior solution to 5.56 mm NATO that it deserves a wider military audience. I wonder how long before it gets the recognition it deserves?

Going back to the original title of this thread, perhaps all the Grendel needs is a military spec bullet that penetrates intermediate barriers, yaws quickly in soft tissue and is reliable in machine guns (by virtue of having a cannelure).

[JASmith]

Guardsman, that is the most succinct and lucid argument for an intermediate caliber that I have hear.

Thanks!

[Guardsman26]

Guardsman, that is the most succinct and lucid argument for an intermediate caliber that I have hear.

Thanks!

I'm not sure about that, but thanks anyway!

I am a real fan of the Grendel - it's the best attempt to produce an intermediate cartridge since the UK 6.25 mm and US 6 mm SAW of the 1970s - and outperforms both in a smaller package. If it were adopted tomorrow, I'd be delighted. But for that to happen it will need further development...

[JASmith]

Are you thinking of the basic cartridge design, rifles, operations analysis, or something else when you indicate further development is needed?

[Guardsman26]

As it is, the Grendel could replace 5.56 mm tomorrow and be a comprehensively better system - but it cannot replace 7.62 mm, so this larger calibre would need to be retained. The opportunity not to miss is that with not much more development work, the Grendel could easily replace both 5.56 mm and 7.62 mm.

This is important. It is a hard sell to get Big Army to adopt a calibre that is heavier than 5.56 mm, but if the weight saving versus 7.62 mm approaches 25%-30% then it becomes compelling. This is the challenge of Grendel development: match 7.62 mm close enough for 6.5 mm to replace this larger calibre as well as 5.56 mm, with the added benefits of simplified battlefield logistics, simplified procurement, lower training requirements and lower spare parts costs.

So what to do? There is nothing wrong with the design of the 6.5 mm bullet. For EU armies however, it's OTM construction isn't acceptable. Design a steel-core projectile with the same G7 FF and BC in a FMJ design that yaws rapidly in soft tissue and you'll be able to pierce level III and IV body armour, which NATO 7.62 M80 ball and NATO 5.56 mm M855 / SS109 presently struggle to do at longer ranges - then you're in business. The present 6.5 mm bullet often doesn't yaw quick enough. The bullet also needs a cannelure to ensure reliable operation in machine guns. Cannelures aren't very good for aerodynamic efficiency. So a military spec 6.5 mm bullet is likely to lose energy more rapidly than its civilian OTM counterpart. Let's not forget that mass-produced military ammo is generally less good than match quality ammo.

This brings us to job two. I believe the Grendel case needs to extended by 10%-15% to give it the extra powder capacity to to get it to MV of around 900 mps when fired from 16" barrels - entirely possible with a 7 g bullet. This results in a cartridge that is identical to what we have now but is slightly longer at around 64 mm. This would very similar to the 6 mm SAW round of the 1970s except for the fact that the calibre is slightly larger. Give the case a less pronounced shoulder to aid MG feeding and extraction and you make it even better.

The big issue here is that as soon as you extend the cartridge length, you need an AR10 platform not an AR15 platform. Since current Grendel weapons are close to the limit of the AR15's limits, that might not be a bad thing. Let's not forget that military shooting can be much more testing on a weapon's components than shooting foxes in your back yard. A heavier weapon also helps mitigate felt recoil, but the overall weight should be somewhere between an AR15 and an AR10, say 3.8 kgs. In a machine gun, however the weight saving would be considerable. A 7.62 mm Minimi converted to 6.5 mm could weigh less than 8 kg. Compared to an 11-12 kg MAG 58 GPMG in 7.62 mm and that's very worthwhile. And let's not forget, reducing the MG ammo load carried by the squad by 25%-30% is huge, especially when they're carrying 2,000-3,000 rounds:

Moreover, a squad equipped with with 6.5 mm weapons could take on one equipped with 7.62 mm and outrange them while the latter would run out of ammo sooner. That's what I call overmatch.

It doesn't take rocket science to do this. I'd like to see Bill A develop a SuperG.

[JASmith]

Would you accept a solid brass or copper bullet as a surrogate? The overall density in only a little more than a steel-cored copper bullet would be, especially the brass bullet. There are custom bullet makers who will make any shape we want as long as we don't run afoul about Federal restrictions on 'armor-piercing' ammunition. My thinking is that we can address both the Federal issue and the weight matching by using a soft brass and drilling a hollow point.