Grendel as a Universal Infantry Cartridge

[LRRPF52]

I agree with you it shouldn't be used as a replacement for the M4 but I don't think it has enough case capacity/power for use in a LMG either.

A 130gr at 2550-2600fps with a long COL is totally doable with another bolt design, especially when you look at canister powders specifically for it. BjornF16 developed a load for his Savage 20" bolt-action Grendel with the 129gr Interbond on top of CFE, and was able to hit 2585fps before the velocities starting getting erratic. He used a longer COL of 2.350". If you went to 2.400" in a belt-fed, you could even get more case capacity.

As it stands, that a 130gr at 2585fps with a .550 BC over-takes the .311 147.8gr 7.62x54R at 2750fps by 150yds for speed, and matched energy by 275yds. Trajectory and wind drift are significantly less, as is recoil and soldier's load. I consider this over-match, especially since we use belt-feds for busting through barriers in MOUT, and picking up where the carbines leave off in open terrain, while also being used in blocking positions to interdict vehicles.

130gr 6.5mm with .550 BC

       Range    Velocity    Energy     Trajectory         TOF          Drift
      (yards)     (fps)     (ft-lb)       (MILS)         (sec)         (MILS)
          0      2585        1929           0.00         0.0000         0.00
         25      2544        1868          -1.51         0.0292        -0.05
         50      2504        1809          -0.31         0.0590        -0.09
         75      2464        1752          -0.04         0.0891        -0.14
        100      2424        1696          -0.00         0.1198        -0.19
        125      2385        1642          -0.06         0.1510        -0.23
        [B]150      2346[/B]        1589          -0.17         0.1827        -0.28
        175      2307        1537          -0.31         0.2150        -0.33
        200      2269        1486          -0.48         0.2477        -0.38
        225      2231        1437          -0.65         0.2811        -0.43
        250      2194        1389          -0.85         0.3150        -0.49
        [B]275      2157[/B]        [B]1343[/B]          -1.05         0.3494        -0.54
        300      2120        1297          -1.26         0.3845        -0.59
        300      2120        1297          -1.26         0.3845        -0.59
        350      2048        1210          -1.71         0.4565        -0.70
        400      1977        1128          -2.19         0.5310        -0.82
        450      1907        1050          -2.70         0.6083        -0.94
       [B] 500      1839         977          -3.24         0.6884        -1.06[/B]
        550      1773         908          -3.82         0.7714        -1.19
        600      1709         843          -4.42         0.8576        -1.32
        650      1646         782          -5.06         0.9470        -1.45
        700      1586         726          -5.74         1.0399        -1.59
        [B]750      1527         673          -6.45         1.1363        -1.74[/B]
        800      1471         624          -7.20         1.2364        -1.88
        850      1417         579          -8.00         1.3403        -2.04
        900      1366         538          -8.84         1.4482        -2.20
        950      1317         501          -9.73         1.5601        -2.36
       [B]1000      1272         467         -10.67         1.6761        -2.52[/B]
       1050      1229         436         -11.66         1.7961        -2.69
       1100      1190         409         -12.71         1.9202        -2.86
       1150      1154         384         -13.82         2.0483        -3.04
       [B]1200      1121         363         -14.98         2.1803        -3.21 still supersonic[/B]
       1250      1092         344         -16.20         2.3160        -3.39
       1300      1066         328         -17.49         2.4552        -3.56
       1350      1042         313         -18.84         2.5977        -3.74
       1400      1020         301         -20.25         2.7434        -3.91

147.8gr 7.62x54R Light Steel Core, .325 BC

       Range    Velocity    Energy     Trajectory         TOF          Drift
      (yards)     (fps)     (ft-lb)       (MILS)         (sec)         (MILS)
          0      2750        2485           0.00         0.0000         0.00
         25      2679        2358          -1.56         0.0276        -0.07
         50      2608        2236          -0.34         0.0560        -0.14
         75      2539        2119          -0.05         0.0852        -0.22
        100      2471        2006          -0.00         0.1151        -0.29
        125      2404        1899          -0.05         0.1459        -0.37
        150      [B]2338[/B]        1796          -0.15         0.1775        -0.45
        175      2273        1698          -0.29         0.2100        -0.54
        200      2209        1604          -0.45         0.2435        -0.62
        225      2146        1514          -0.63         0.2779        -0.71
        250      2085        1428          -0.82         0.3134        -0.80
      [B]  275      2024 [/B]       [B]1346[/B]          -1.03         0.3499        -0.89
        300      1964        1267          -1.26         0.3875        -0.98
        325      1905        1193          -1.50         0.4263        -1.08
        350      1848        1122          -1.75         0.4663        -1.18
        375      1792        1055          -2.01         0.5075        -1.28
        400      1736         991          -2.29         0.5500        -1.39
        425      1683         930          -2.59         0.5939        -1.50
        450      1630         873          -2.90         0.6392        -1.61
        475      1579         820          -3.22         0.6859        -1.73
       [B] 500      1530         769          -3.56         0.7342        -1.85[/B]
        525      1482         722          -3.92         0.7840        -1.97
        550      1436         677          -4.29         0.8354        -2.09
        575      1391         636          -4.68         0.8885        -2.22
        600      1349         598          -5.09         0.9432        -2.35
        625      1308         562          -5.53         0.9997        -2.49
        650      1270         530          -5.98         1.0579        -2.63
        675      1234         500          -6.45         1.1178        -2.76
        700      1200         473          -6.95         1.1795        -2.91
        725      1169         449          -7.47         1.2428        -3.05
        [B]750      1140         427          -8.02         1.3078        -3.19[/B]
        [B][COLOR="red"]775      1113         407          -8.59         1.3744        -3.34[/COLOR][/B][B]subsonic[/B]
        800      1089         390          -9.18         1.4426        -3.48
        825      1066         374          -9.80         1.5122        -3.63
        850      1046         360         -10.45         1.5833        -3.78
        875      1027         347         -11.12         1.6557        -3.92
        900      1010         335         -11.82         1.7293        -4.06
        925       993         324         -12.55         1.8043        -4.21
        950       978         314         -13.30         1.8804        -4.35
        975       963         305         -14.08         1.9578        -4.49
       [B]1000       949         296         -14.88         2.0363        -4.62[/B]
       1025       936         288         -15.71         2.1159        -4.76
       1050       924         280         -16.57         2.1967        -4.90
       1075       912         273         -17.45         2.2785        -5.03
       1100       900         266         -18.36         2.3614        -5.16
       1125       889         260         -19.29         2.4454        -5.30
       1150       879         254         -20.25         2.5304        -5.43
       1175       869         248         -21.24         2.6164        -5.56
       1200       859         242         -22.25         2.7035        -5.68
       1225       849         237         -23.29         2.7916        -5.81
       1250       839         231         -24.35         2.8807        -5.94
       1275       830         226         -25.44         2.9708        -6.06
       1300       821         222         -26.56         3.0620        -6.18
       1325       812         217         -27.70         3.1541        -6.31
       1350       804         212         -28.87         3.2473        -6.43
       1375       795         208         -30.06         3.3416        -6.55
       1400       787         204         -31.28         3.4368        -6.67

As a Squad Leader, I would have loved to have had that type of performance in a true Light Machine Gun, with linked ammo the equivalent weight of 7.62x39 linked. Add in a DM per Fire Team with an SPR-type rifle with these capabilities, and reacting to contact in a mountainous environment takes on new meaning, where my trained killers can actually get some performance at distance, as opposed to 5.56 peeing in the wind.

With that load, I'm supersonic out to 1200yds, and they are subsonic by 775yds.

[Trooper]

OK -- I just have to ask.

How many RIFs did you live through in your Army career?

How about showing us proof that boards are in the process of removing Officers and NCO's who are 'non-compliant'.

I am sure that since you believe a 'purge' of 'non-compliant' officers is going on, that you can link us to a Dept of the Army web site that has a copy of this compliancy list and states how to look at a 201 file or OER and determine if an Officer is or is not 'compliant'.

LR1955

Army Times has had a number of cover articles over the last 6 weeks on the shrinking size of the US Army.

The real problem is that we are pulling back. We may no longer afford to project power abroad.

The Islamists moved to fill the void in the power vacuum left after the collapse of the Soviet Union. I have wondered who would fill the void if we no longer are a super power. My guess is that China will take our place. It will be then that most of the resources in the world will come under the control of either China or the Islamists. And we will have to decide who we seek to be ruled by.

[LRRPF52]

China as a superpower is a myth propagated by disinformation sources that don't have any reputable assets in China to actually report on the ground truth there.

The US has maintained a force presence on the world's sea lanes since before the Second World War, and assumed an even larger one after the shrinking of the British Empire. China shares borders and critical coastline with:

Russia                   India
Mongolia                Nepal
North Korea            Kazakhstan
South Korea           Kyrgyzstan
Japan                    Tajikistan
Philippines              Afghanistan
Vietnam                 Pakistan
Taiwan                   Bhutan
Myanmar                Tibet
Laos

http://www.investorsinsight.com/blogs/john_mauldins_outside_the_box/archive/2008/06/12/the-geopolitics-of-china.aspx

Maybe one out of 10,000 people you will ever meet is even remotely familiar with Chinese geography, their constraints, history, population, demographics, or politics. No matter what they do, they will never even come close to the physical capacity to deploy a navy or air force with the capabilities that the US has, because they simply don't have the sea ports to make it happen. China has the second largest concentration of deep sea ports along its coast in the world, which is about 1/3 of that the US's is. Northern Europe as a region would be next on that scale.

While China is clearly on an expansionist binge, scrambling for every resource, trade deal, and foreign mineral exploitation operation, they face monumental population, demographic, social, and political challenges that manifest themselves daily. As of 2011, they had experienced over 200 internal revolts against local corrupt governments, for example. With a population of 1.347 billion occupying land area that is less than half of the US, you can start to see how that's a reality.

They are also the historical authors of asymmetric warfare if you read Sun Tzu. Asymmetric warfare means that small arms will play an important, but peripheral role to intelligence and force flexibility.

Interesting to the discussion, China attempted to adopt a universal infantry cartridge system with the 5.8x42mm, which is lacking in long range performance, and is a bit long for an individual service rifle:

5.8x42mm on the right


I suspect they did this for ease of logistics purposes, and their propaganda services stated that it was to prevent "invaders" from being able to use common ammunition, which their Warsaw Pact chambered weapons would technically allow.

[woohoo]

A 130gr at 2550-2600fps with a long COL is totally doable with another bolt design, especially when you look at canister powders specifically for it. BjornF16 developed a load for his Savage 20" bolt-action Grendel with the 129gr Interbond on top of CFE, and was able to hit 2585fps before the velocities starting getting erratic. He used a longer COL of 2.350". If you went to 2.400" in a belt-fed, you could even get more case capacity.
.

Do you know how long a 130gr 6.5 green bullet would be? If you want a 130gr green bullet you'll need to step up to a 7mm at least. I know some hate the green thing but the mil is going that way like it or not.
On top of the new green bullets all new cartridges will need to be designed for poly or lsat which is thicker than brass. The operating pressures should be kept down to 55k psi max in 110 degree temps. That is the spec that killed the 6.8s performance and reason Remington downloaded their ammo.
The cases used in MGs should have more taper than the Grendel which will also reduce the capacity.
We've been talking about bullet designs on Tonys forum for months. Mass production, terminal performance and BC must be considered. Also if too heavy they will not meet the weight reduction requirements, if to light they will not have the terminal performance. Using litz's perfect bullet design which with lead core bullets usually end up with a .675 BC, the optimum design is apx 5 calibers long. A 6.5 ends up in the area of 110-115gr when green. The 6.8 bullets range 118-123gr and the 7mms 125-130gr. All bullets regardless of caliber can have the same BC when using the same formula Litz uses. It seems to me the weapons the military are having produced have shorter barrels. The MK48s being reworked now have barrels shorter than 20" according to the company reworking them. All of that works against smaller cartridges. IMO Murray did the research and came up with the right idea for a LMG cartridge that will perform better than the 7.62x54 at range while giving close to the same terminal performance.

[Tony Williams]

Do you know how long a 130gr 6.5 green bullet would be? If you want a 130gr green bullet you'll need to step up to a 7mm at least. I know some hate the green thing but the mil is going that way like it or not.

Not necessarily: the Barnes 6.5mm 126.5 grain LRX bullet is solid copper with a hollowpoint filled with a polymer tip. It measures c.35mm long (the same as a lead-cored 6.5mm 140 grain Berger VLD) which gives a length/diam ratio of around 5.2. The problem comes when you want a tracer version of the bullet….

Incidentally, the LRX has a G7 BC of .460, a G1 of .230 while the Berger's numbers are .612 and .313 respectively - the cost of going lead-free! OTOH the LRX will have a higher MV due to the reduced weight, even though the propellant space will be about the same.

[SHORT-N-SASSY]

Tony Williams,

Thank you for your clarification.

1, Using identical projectile style, how much longer would a 130-grain .264" diameter projectile be vs a 130-grain .277" diameter projectile?
2, To maintain the same length of a 130-grain .277" projectile, what weight would the .264" diameter projectile have to be?

[JASmith]

The 130 grain interest comes from the notion that retained energy is an important parameter for projectile effectiveness. It is not.

The closest the total energy at impact comes to having a significant effect is the sound and size of splash heard and seen by troops near it. This is, at best, a weak argument mostly because any splash or noise will get their attention if they know that serious or lethal injury will result if they get hit.

We know that bullets of weighing 60 grains or more are highly effective on live targets.

The remaining issue is total penetration through timbers and hard targets. Here the useful metrics are the momentum and momentum densities which are the sectional densities multiplied by the velocity or square of the velocity.

The 6.5 does very well, especially at long ranges. compared to the 7.62 Russian and 7.62 NATO when these metrics are employed.

Hence, we can go with a green bullet weighing 95-100 gr for an infantry carbine and 110-120 gr for the LMG.

We might not need to invoke a longer COL for the LMG -- just accept pressures of 55,000 to 60,000 psi to get excellent long range performance. This would maintain emergency ammunition interoperability to cover those exceedingly rate events when one type or another is not available.

[Michael]

The remaining issue is total penetration through timbers and hard targets. Here the useful metrics are the momentum and momentum densities which are the sectional densities multiplied by the velocity or square of the velocity.

If anyone is interested in bullet penetration, here is a link to a video on a test done a few years ago

http://www.liveleak.com/view?i=29d_1318009976

My experience in the 3d world is 5.56 punches through shanty town buildings with no issues (think Somalia), and .50 BMG/HMG has a hard time getting through some of the think mud walls (Afghanistan/Iraq). This goes back to the premise posed by LRRPF52 as to where we will fight...and I agree wholeheartedly with his assessment. Asymmetric urban environment in the littoral regions.

[Tony Williams]

Tony Williams,

Thank you for your clarification.

1, Using identical projectile style, how much longer would a 130-grain .264" diameter projectile be vs a 130-grain .277" diameter projectile?
2, To maintain the same length of a 130-grain .277" projectile, what weight would the .264" diameter projectile have to be?

I don't know - I was just looking at illustrations of actual bullets, I don't have a bullet design program.

[woohoo]

Tony,
Why don't you get all of the test data in a poly version together and present it at the NDIA meeting. That would be a start at getting everyone to consider it for CLAWS.

[Tony Williams]

I'm probably not going to the next NDIA - it clashes with something else I want to do.

[BluntForceTrauma]

If you've got a .308, PCP Ammunition is looking for testers of their polymer-cased .308.

John

[LRRPF52]

Here's the link for the civilian testing: http://www.pcpammo.com/limited

[Trooper]

At least someone is developing a polymer case. It makes no sense to leave brass on the battlefield. Polymer is lower cost and lighter weight. Even against aluminum or steel cases.

[Trooper]

One thing. With comparison to the .308, the 6.5x55 Swede is the standard. Thus the .260 Rem or the 6.5mm Creedmoor come close. The 6.5x47 Laupa comes up a bit short. The standard is to move a 6.5mm round weighting 140 gn. at 2550 fps out of the barrel. That would be equivalent to the .308 with a 192 gn. bullet. http://www.eabco.com/6.5_mm_cartridges.html

Thus it would be difficult to make a round that would fit into a standard M4 magazine well that would be able to compare to the 6.5x55. Especially using a 140 gn. bullet. Thus we would be using a smaller round but might be able to do about 80% of what the .308 does. With a lot less recoil.

If we need a heavier round for a medium MG, the .338 NM (8.6x63) would do. the .338 has a similar BC (.600) to what the 6.5mm has.