Military round comparisons

[Variable]

The bullet, which has an ideal form factor, is very long - but you really wouldn't want to change that. What we really need is increased powder capacity to give it a little extra energy and thus retained energy at long range - especially when fired from short-barrel weapons - and better short-range terminal effectiveness, including barrier defeat. In other words, what the Grendel really needs is a slightly larger case - something in between the current 11.3 x 39 mm and the 6.5 mm x 47 Lapua brass.

First--- Welcome to the Grendel boards!

Second--- Extra energy as compared to what? Increased barrier penetration as compared to what? The 6.5 Grendel is capable of defeating a level 4 rifle plate as is when loaded with an AP round. How much barrier penetration do you possibly need?

Remember, increased energy comes with increased recoil. The way our politically correct militaries are heading, the average Sheila won't be able to handle them if you jack it up too much.

What numbers are you looking for?

[LRRPF52]

The bullet, which has an ideal form factor, is very long - but you really wouldn't want to change that. What we really need is increased powder capacity to give it a little extra energy and thus retained energy at long range - especially when fired from short-barrel weapons - and better short-range terminal effectiveness, including barrier defeat. In other words, what the Grendel really needs is a slightly larger case - something in between the current 11.3 x 39 mm and the 6.5 mm x 47 Lapua brass.

Welcome. We've kicked this horse before many times. Actually, the Grendel case capacity isn't really a limiting factor as much as the AR15 bolt is, but it helps keep the pressure at a level that increases longevity of the throat & barrel over 7.62x51 weapons, which have an excellent barrel life.

As far as logistics goes, we already have several different loadings for the 5.56 weapons, to include:

M193 (mostly phased out, but an excellent loading for CQB to 200m)
M855 (for the SAW, then M16A2)
Mk 262 & variants for DM's
M855A1

That's not even addressing the 7.62 variants in the US system. I personally believe the M855A1 will serve more as a way to break us economically, despite the claimed improvements in performance. The best cartridge you can possibly ever have is the one that you can train with the most.

Back to the Grendel's case capacity. It will take way more pressure than the AR15 bolt will, so there is plenty of capacity. For a military weapon that is designed to take more pressure if you really felt you needed it, you could use a bolt with more mass to it, and more bearing surfaces on the locking lugs. I used to think something like that would be worth pursuing as a solution, but the problem really doesn't exist.

I don't want every swinging Richard with a 130gr hot load, doing its best to reach 7.62 recoil impulse. Carbines should track well on-target, and 5.56 provides that in spades. A purpose-designed powder for a light 6.5 load for carbines, maybe pushing even an 85gr-95gr bullet at 2800fps would be more than adequate for Joe Tentpeg's consumption, but I'm perfectly happy with keeping 5.56 in carbines.

LMG's and DMR's are where we need the Grendel, so we could phase out 7.62 NATO for dismounts.

[stanc]

Extra energy as compared to what? Increased barrier penetration as compared to what?

Compared to 6.5 Grendel, of course.

Guardsman and others want a true general purpose cartridge, and consider 6.5 Grendel to be not quite powerful enough for that mission.

[Guardsman26]

Compared to 6.5 Grendel, of course.

Guardsman and others* want a true general purpose cartridge, and consider 6.5 Grendel to be not quite powerful enough for that mission.

(Tony Williams - who else?)

Absolutely right, Stan. Thank you for pointing that out. And the SF community is seriously interested in a weapon in a calibre that can deliver the associated benefits.

The Canadian paper study presented at Shrivenham last year showed just how effective the Grendel could be - when fired from a weapon with a 24" barrel. It has done much to re-ignite the calibre debate in military circles.

However, as soon as you fire the existing 6.5 Grendel from a weapon with a 16" barrel, retained energy levels drop-off alarmingly - to the point where the Grendel offers no appreciable difference versus 5.56 mm. This has been tested and validated by at least two mainstream manufacturers. (It may also explain why Dr. Gary Roberts gel tests were inconclusive). Hence my view that a slightly longer cartridge with increased powder capacity would easily overcome the problem and provide a true GPC round.

One of the other things I've been looking at is whether an extended version of the 6.8 mm Remington SPC case would be a better alternative to an extended Grendel case. While it would create a longer, more slender round, as LRRPF52 points out, the Grendel case can take more pressure. So, the 39 mm 11.3 mm case is the right one to extend IMO.

I like everything about the Grendel round except case length. A long case with a less pronounced shoulder would also facilitate easier feeding.

[LRRPF52]

However, as soon as you fire the existing 6.5 Grendel from a weapon with a 16" barrel, retained energy levels drop-off alarmingly - to the point where the Grendel offers no appreciable difference versus 5.56 mm.

This is incorrect. I have a 16" Grendel, and it has produced 24" velocities with certain factory ammunition. Even at pressures under 50,000 psi, the 16" Grendel is no joke, sir. It does not drop off alarmingly from a 24" barrel, velocity-wise. You're looking at 18fps average difference per inch of barrel loss from a 24".

16" Grendel with Current Civilian 123gr Target Load at 2450fps

Code:

Range Velocity Energy Trajectory TOF Drift (yards) (fps) (ft-lb) (MILS) (sec) (MILS) 0 2450 1639 0.00 0.0000 0.00 50 2357 1517 -0.32 0.0624 -0.12 100 2266 1402 -0.00 0.1273 -0.24 150 2177 1294 -0.21 0.1949 -0.37 200 2090 1192 -0.57 0.2652 -0.50 250 2004 1097 -1.00 0.3385 -0.63 300 1921 1008 -1.50 0.4149 -0.78 350 1839 924 -2.03 0.4947 -0.93 400 1760 846 -2.62 0.5781 -1.08 450 1681 772 -3.24 0.6653 -1.24 500 1605 703 -3.91 0.7566 -1.41 550 1529 639 -4.63 0.8523 -1.59 [B]600 1456 579 -5.41 0.9528 -1.78[/B] 650 1384 523 -6.23 1.0585 -1.98 700 1314 472 -7.12 1.1698 -2.19 750 1246 424 -8.08 1.2870 -2.40 800 1181 381 -9.12 1.4107 -2.64 850 1120 343 -10.23 1.5412 -2.88 900 1074 315 -11.44 1.6782 -3.13 950 1045 298 -12.73 1.8200 -3.38 1000 1020 284 -14.12 1.9654 -3.62

24" Grendel with same 123gr Target Load at 2600fps

Code:

Range Velocity Energy Trajectory TOF Drift (yards) (fps) (ft-lb) (MILS) (sec) (MILS) 0 2600 1846 0.00 0.0000 0.00 50 2504 1712 -0.36 0.0588 -0.11 100 2409 1585 -0.00 0.1199 -0.22 150 2317 1466 -0.16 0.1833 -0.34 200 2227 1354 -0.46 0.2494 -0.46 250 2139 1249 -0.83 0.3181 -0.58 300 2052 1150 -1.26 0.3897 -0.71 350 1968 1058 -1.73 0.4643 -0.85 400 1885 971 -2.24 0.5422 -0.99 450 1805 889 -2.78 0.6235 -1.13 500 1725 813 -3.37 0.7085 -1.29 550 1648 742 -3.99 0.7975 -1.45 [B]600 1572 675 -4.66 0.8907 -1.62[/B] 650 1497 612 -5.38 0.9884 -1.80 700 1424 554 -6.15 1.0911 -1.98 750 1353 500 -6.98 1.1992 -2.18 800 1284 451 -7.86 1.3130 -2.38 850 1218 405 -8.82 1.4329 -2.60 900 1154 364 -9.85 1.5595 -2.83 950 1097 329 -10.96 1.6930 -3.07 1000 1060 307 -12.16 1.8323 -3.32

At 600yds, you see the practical difference between the two is 1.6 Mils of wind deflection for the 2600fps load, and 1.8 Mils for the 2450fps load...a whopping .2 Mils. Trajectory is 4.7 Mils for the 2600fps load, and 5.4 Mils for the 2450fps load, or a .7 Mil difference, which is noteworthy, but just a different hold for the shooter. Again, with the right powder/system, we can run the 16" gun at 2600fps with a 123gr if we really want to, but do we need to?

You can also safely run a current 16" Grendel with 100gr projectiles at 2700fps. Bill A. himself has told me that analyzing only muzzle velocities across a large population of 20" and 24" guns, you will not be able to identify which ones were 24" and which ones were 20", as they overlap each other, so a 24" is totally unnecessary for military applications.

Again, you really don't need a longer, bulkier, heavier case to drive any weight of projectile from 85gr-130gr from the current Grendel case. It will take insane levels of pressure in the right gun with a larger bolt, but do we really need that kind of pressure? No we do not.

I can also assure you that a 16" Grendel is an entirely different animal than even a 20" 5.56 NATO. Energy on-target and wind deflection are different ball games with the Grendel. You're looking at diminishing returns by increasing the case length, with increasing penalties. Bulk, recoil, barrel life, and weight are the penalties, leaning towards a 6.5x47 Lapua, which is super over-kill for a GPC.

If you want to increase the pressure to 54,000 psi, using a larger bolt would solve that requirement, and no larger case would be needed. With an industrial powder, you could easily run a 130gr projectile at 2550-2600fps, maybe faster. One of the forum members has achieved 2700fps with the 130gr Norma Golden Target using CFE223 powder out of his 24" Grendel, loaded to 2.300" COL, fed from the mag.

If you run the numbers, you'll see just how little these differences in barrel length and downrange performance equate to each other. The UK would be better off with a Gen II LMT MRP system on the AR15 frame (not the AR10/7.62 NATO), chambered in 6.5 Grendel for DM's, along with a new Multi-Role LMG chambered in 6.5 Grendel. Both systems would use a purpose-designed bolt with larger lugs, without worry of compatibility with the US AR15 civilian market.

I have spoken extensively with Lapua's R&D personnel, and they have run the Grendel from a bolt gun at frightening pressures, delivering 3400fps with 123gr Lapua Scenars, to see just how much the case can take. They exceeded .300 Winchester Magnum pressure limitations by 15%, and the brass was trashed, but didn't fail.

Nobody wants or needs anything close to those pressures from the Grendel. A 16" gun is just fine, with a purpose-build industrial powder and military load, within the AR15 receiver set size and existing magazine profile. The 7.62x51 LMT L129A1 system is a beast to carry, and a Grendel replacement would be very welcome to the lads, plus they would get a magazine capacity increase as well.

If you keep the loading at current Grendel pressures, you end up with a weapon life cycle much longer than one that runs higher pressures, and a powder could be developed specifically for it to get the velocity you need, without peaking the pressure much above 50,000psi.

[JASmith]

The other problem is that "energy" alone does not adequately describe a weapon's potential.

As others have pointed out already, recoil energy or impulse needs to be kept down for the average soldier to have a good chance at a semblance of marksmanship.

This topic has been beat to the ground a bunch of times already.

The laws of physics and current chemistry drive us to certain classes of solutions where there exists very little difference between many alternatives. Hence, adding 5,000 psi or 5 gr powder capacity may up the velocity a few percentage points at the cost of increased recoil, logistics burden, or both. The downrange performance as measured in drop, drift, and terminal effects, however remains effectively the same.

If one really wants to surpass the Grendel or the several other cartridges like the 6.8 SPC, the 7mm variants discussed in MG&A, new approaches to cartridge, bullet, and firearms design need to be implemented.

[Nukes]

No, I haven't seen any for sale. I think they'd be post samples anyway though. I don't think they are made anymore.

I also think it would likely make a great Grendel platform, and have brought it up multiple times in the past here and on the old board.

http://www.forgottenweapons.com/wp-conte...ndbook.pdf

Another great possible candidate (IMHO) would be the Ares Shrike, but it would have to belong to someone other than Ares to ever happen.... I have one in 5.56, and it's an awesome concept, but being produced by Ares severely hampers it.

Intriguing. I have only the barest knowledge of the Ares Shrike. Beyond the bolt and links, I am curious how major a redesign would be necessary for 6.5 Grendel.

[JASmith]

...However, as soon as you fire the existing 6.5 Grendel from a weapon with a 16" barrel, retained energy levels drop-off alarmingly - to the point where the Grendel offers no appreciable difference versus 5.56 mm...

This is a rather extreme statement and needs to be expanded.

As you think about how to expand, let's make sure terms are adequately defined so that we can either enthusiastically agree or respectfully disagree. Examples of areas where terms and performance levels need to be defined are:

* What is meant by "appreciable?"

* Engagement range under consideration -- are we talking close quarters battle, 200 meters, or ranges where designated marksmen and snipers predominate?

* Desired barrier perforation -- do we discuss absolute or comparative? Comparative means that one doesn't have to go beyond sectional density and impact velocity to get significant insight.

* Numbers of rounds carried -- some feel the 5.56 has a big advantage in this area while others feel longer range trajectory and terminal effects are important.

Further, you should use this barrel length vs velocity estimator to get a feel for how velocity changes with barrel length on average.

I can say that the wind drift for 14.5" Grendel at 500 meters tends to be less than the wind drift of ta 22" barreled .243 Winchester and that the Grendel bullets hit harder. A 16" barrel on the Grendel does better of course.

In this category, one would be hard pressed to accept arguments that the 5.56 and Grendel are relatively indistinguishable.

I would, however, accept the argument that there is no appreciable difference in terminal effects and trajectories inside 250 meters against unarmored humans.

So, let's get terms defined and a productive discussion underway before some of your readers respond more from emotion than with knowledge and understanding.

[BjornF16]

Look forward to Guardsman26's response...I'm not sure there is "appreciable" difference between 14.5" and 16" Grendel ...20 - 30 fps?

[LRRPF52]

I think the curve starts to take a dip between 16" and 14.5", but not so much between 14.5" and 12.5". Just like a 16" and 18" are hard to distinguish from each other, just like a 20" and 24" are indistinguishable when looking at velocities. 14.5" velocities for a 123gr AMAX are 2350fps, while they are 2450fps from a 16". The best velocity Hornady lists with the 123gr AMAX is 2500fps from an 18". The average loss I have seen with identical loads between a 24" and 16" was 18fps.

My suspicion is that this is a factor of gas system length, more than just barrel length. You'll notice that the guns that use rifle-length gas systems produce the same velocities (20", 22", and 24"), just like the mid-lengths (18" & 16"), and carbine lengths (14.5" & 12.5"). If true, the argument can be made that the shortest barrel length practical with the gas system used is most efficient.

[JASmith]

I suspect that folks are confusing barrel lengths when comparing velocities. Some folks use 24" for testing. Others shorter barrels.

So, a manufacturer reports data for a 16" barrel, the reader thinks it is a 24" and subtracts the usual 150-200 ft/sec and says "Holy Cow, those velocities a really low!" The problem is they tend to not go back and cross check sources, so they think they are arguing from fact when they using erroneous information to slander a cartridge.

[Tony Williams]

Of course, if a long barrel is needed to extract the performance you want without going to a bigger and more powerful cartridge, then there's an obvious answer...work on a decent* bullpup design, and enjoy a 20 inch barrel in a gun the same overall length as an AR-15 with a 10-12 inch barrel.

*fully ambidextrous without having to dismantle and rebuild the gun, and with an adjustable stock length.

[LRRPF52]

Only problem is that there are no decent bullpup designs. I like the Steyr AUG the best, but alas, it has a plastic trigger...really?

The 20" barrel isn't really necessary in today's age of powders, especially for a general-purpose service cartridge. I'm a huge fan of the bullpup concept. The code to achieving fully ambidextrous use with one has yet to be cracked, and that especially includes the modern copies of the Russian ТКБ-022ПМ № 2 Bullpup ejection system.





I have some designs that tackle this, but the problem of feeding it with a standard military cartridge from feasible magazines, and managing the ejection, while incorporating AR15-type ergos is monumental. A bullpup LMG is another story entirely.

[Variable]

Only problem is that there are no decent bullpup designs. I like the Steyr AUG the best, but alas, it has a plastic trigger...really?

The 20" barrel isn't really necessary in today's age of powders, especially for a general-purpose service cartridge. I'm a huge fan of the bullpup concept. The code to achieving fully ambidextrous use with one has yet to be cracked, and that especially includes the modern copies of the Russian ТКБ-022ПМ № 2 Bullpup ejection system.





I have some designs that tackle this, but the problem of feeding it with a standard military cartridge from feasible magazines, and managing the ejection, while incorporating AR15-type ergos is monumental. A bullpup LMG is another story entirely.

Apologies for OT: The Ruski bakelite shell--- how in the heck does that work? How can they have a bolt that still has room to strip a round out of the mag?

Bullpups: I'm still interested in one also, but I'm with you. They need a real trigger first. I'd still like to see a P90 style weapon in Grendel also. The mag geometry might be tricky or awkward though.

[Variable]

Intriguing. I have only the barest knowledge of the Ares Shrike. Beyond the bolt and links, I am curious how major a redesign would be necessary for 6.5 Grendel.

Not much really. You'd have to tweek the geometry of the tray, topcover components, and bolt.

My arguments with Stan aside (:p), the links should be the biggest obstacle, simply because setting up high volume sheet metal stamping is no task to be taken lightly. You have to be pretty dedicated on that one.

The fact that Ares is so astronomically challenged in just delivering 5.56 guns though is the real world killer. If he can't deliver on 5.56 in any reasonable manner, then Grendel is pretty much out of the question.

It's a shame really IMO. Geoffrey wanted military sales, but I doubt he'll ever see them. If he could actually manufacture like a pro (ala Colt), instead of just making really nifty prototypes that rarely see the market, then he'd be insanely rich by now.

I'd add a bit of mass to the sytem for a trials gun, but a 6.5 Grendel Shrike in about the 10 pound range would be a peach. If I could be General Curtis Lemay reincanated, I'd have my AF Security Forces abduct Bill Alexander and Geoffrey Herring and lock them in a bunker together. I wouldn't let them out until I had the Grendel Shrike. Then I'd pay them a kabillion dollars for the rights, and contract Colt to make it. Done, problem solved. Tada! I'd standardize the round, and then declare I didn't want to here any crap whining until plasma rifles in the 40 watt range are available.LOL

[Variable]

(Tony Williams - who else?)

Absolutely right, Stan. Thank you for pointing that out. And the SF community is seriously interested in a weapon in a calibre that can deliver the associated benefits.

The Canadian paper study presented at Shrivenham last year showed just how effective the Grendel could be - when fired from a weapon with a 24" barrel. It has done much to re-ignite the calibre debate in military circles.

However, as soon as you fire the existing 6.5 Grendel from a weapon with a 16" barrel, retained energy levels drop-off alarmingly - to the point where the Grendel offers no appreciable difference versus 5.56 mm. This has been tested and validated by at least two mainstream manufacturers. (It may also explain why Dr. Gary Roberts gel tests were inconclusive). Hence my view that a slightly longer cartridge with increased powder capacity would easily overcome the problem and provide a true GPC round.

One of the other things I've been looking at is whether an extended version of the 6.8 mm Remington SPC case would be a better alternative to an extended Grendel case. While it would create a longer, more slender round, as LRRPF52 points out, the Grendel case can take more pressure. So, the 39 mm 11.3 mm case is the right one to extend IMO.

I like everything about the Grendel round except case length. A long case with a less pronounced shoulder would also facilitate easier feeding.

So you want "more". Please define this elusive "more".LOL

Example: Penetration--- You do realize that the 6.5 Grendel can penetrate an ESAPI plate with the right AP projectile right? ESAPI stops .30-06 (7.62x63) M2 AP..... What kind of penetration are you realistically seeking? The SD of the 6.5 projectiles is already in your favor.

What velocity? Why?

What B.C.? Why?

How many foot pounds? Why?

When you ask for too much, your troops ability to effectively employ it is reduced. Just my opinion, but I believe the Grendel as-is hits the sweet spot for efficient performance. You'll hit diminishing returns quickly when you try to outdo it.

[Kikn]

Will those plasma rifles come in 6.5 gren? If do put me down for two :p

[Von Gruff]

We need an icon like this for those of us who are interested in the conversation - discussion.

[Tony Williams]

Only problem is that there are no decent bullpup designs.

True, but there are several which come close in different ways.

The Tavor X95 offers an M4-style control layout, even including the mag release, but is not ambidextrous except with a lot of fiddling around.

The STK SAR-21 features a case deflector which means that the gun can be fired left-handed without the user collecting a faceful of hot brass. It also has a kevlar cheekpiece which protects right-handed shooters from collecting the results of a breech explosion.

The latest version of Chinese QBZ95-1 also offers a case deflector and controls very similar to the M4.

The FN F2000 is fully ambidextrous without need to change anything (but has a weird control system).

The Beretta ARX actually has a switchable-side ejection, despite not being a bullpup.

What none of them offers is an adjustable stock length, which would require a shorter mechanism designed to use less space behind the breech (although not to the extreme of the Russian job shown above!).

In other words, it is entirely possible to design bullpups which meet all reasonable requirements. And at the same time it would be worthwhile incorporating a recoil-smoothing mechanism like the Russian balanced-piston type used in the AK-107. If I had a spare few million pounds I'd go to one of the good gunmakers and pay them to develop a bullpup to my specifications.

Some more detailed thoughts on this issue: http://www.quarry.nildram.co.uk/bullpups.htm

[stanc]

Not much really. You'd have to tweek the geometry of the tray, topcover components, and bolt.

My arguments with Stan aside (:p), the links should be the biggest obstacle, simply because setting up high volume sheet metal stamping is no task to be taken lightly.

What arguments? I agree that links are the biggest obstacle to a belt-fed Grendel, although I think design is the issue of concern. Manufacture is just a matter of $$$.