What about FN .264 LICC?

[LRRPF52]

If you are starting with a blank'ish slate for the rifle and magazine there is no reason to compromise with the Grendel case. Grendel's case diameter is great, it's case capacity isn't. Add four or five grains capacity to a bolt that will allow 62kPSI of pressure. I like Grendel but when you take it out of the AR15 it makes zero sense.

The compactness of the AR-15 has been a great limiting stick though to force the industry to develop higher performance cartridges that still fit within a magazine that is easy to carry on soldier’s load. Once you depart from that basic form factor for the magazine, the pouches and soldier’s load suffers. A lot of people might see this and only have reference to a mag pouch or two on their range belt, never having had to hump a basic load or basic load plus, in addition to all the rest of their duty position-specific equipment (Radios, Medic Bags, breaching tools, demo, Anti-Tank weapons, linked 7.62 on gun teams, tripods, T&E mechanism, 40mm Grenades, smoke grenades, grenades, Night Vision, etc.). This is why the 6.8x51 is an abortion even if they had a great weapon design, which they don’t.

This is why I have been more of an advocate for Grendel replacing 7.62 NATO. Similar concept as replacing 50 BMG with 338 Norma Mag.

5.56 is a very inefficient case that wastes a lot of powder, so it’s too long for what it delivers. We could replace 5.56 with something smaller in overall length, and deliver better performance with a look at bore diameter, case design, and propellant. KAC/Hornady already showed that with the 6x35 PDW. (.221 Fireball necked up). You can carry a bunch of those 6x35 KAC PDW mags, almost like M2 Carbine mags.

The .264 LICC is a good compromise getting us away from the 7.62 NATO form factor battle rifle cartridge though. It would be far superior in DM Carbines and LMGs, and would make a nice changeover with NATO coordination for a new set of weapons based on it in those roles. I think 5.56 will be around until the 2nd Coming though.

 

[Macht]

I would have agreed with you prior to seeing my 1k results and 4DOF comparison. The 100gr ELD-VT isn’t in the 4DOF program, so I used actual 1000yd results with factory ammo from my 17.6” Grendel. You might have mistakenly used the 100gr ELD-M, which is not the same bullet at all. 100gr ELD-VT looks like a 123gr ELD-M, but with less lead inside. Way longer boat tail, ogive, and OAL than the 100gr ELD-M.

Real world data for 18” 6mm ARCs and Hornady’s load data show it maxed at 2550fps from 18” barrel for 103-105gr, and somehow increases with 108gr and 110gr A-TIP to 2575fps. But you see the factory ammo velocity thread here with 16” bolt guns and 18” gas guns, where it was 2408-2590fps across several different AR-15s.

Real world for 18” Grendels with 100gr ELD-VT factory ammo is 2650-2690fps. The BC might be better as well. Something is happening to where they track almost identically once you get out to mid-range. I posted about it before asking people to sanity-check what I was seeing, and nobody responded with any details contrary to that. I’m open to whatever the data shows. I was planning on getting a 6mm AR for a long time, but after everything I’m seeing with the 100-110gr class in 6.5mm, I’m just not seeing any advantages.

The 100gr ELD-VT at 2690fps beats any of the 6mm 103-110gr class at 2575fps, flatter, more impact velocity, less wind drift.

Don't spew easily disproven nonsense:

Values pulled directly from 4DOF (STP, 10mph crosswind)

 

[LRRPF52]

Huh? That's factory Hornady, all of which is loaded at 52ksi. View attachment 8536267
What's really wild is people vastly overestimating the 'piston effect'.

Hornady doesn’t load factory ammo to SAAMI MAP, but more in the high 40ksi region to leave room for their lot MPSM and MPLM. They said as much in a recent podcast where numbers like 47-49ksi were mentioned.

With CFE223 in 6.5 Grendel out of a 16” Enfield-rifled barrel, I went way higher than you would typically see in a pressure ladder test when I first started experimenting with CFE223, and I easily got up to speeds that make bolt guns blush, but I never mass-produced those loads of course.

My 123gr A-MAX load is only 47,302psi doing 2520fps from that 16” barrel.
My 123gr A-MAX load that hit 52,075psi was doing 2572fps from the 16” AA/ER Shaw pipe.

Those were 2.272-2.275” COL loads. Pressures were tested independently in a pressure test breach cut with a mid-life spec reamer from Manson, calibrated over a 6-month period and checked with various factory ammo data sets prior to giving merit to the readings. The factory RSI gauges were replaced with quality transducers recommended by industry sources who do pressure-testing for a living.

The Hodgdon’s new data for 100gr ELD-VT shows the fastest speeds from the lowest chamber pressures with CFE223 and LVR, no surprise. I purposely chase those more efficient powders for the case/bullet combo, not max pressures. I think trying to brute-force the performance with pressure is not really the best way to go about things, especially as armorers, soldiers, and leaders become more technically-incompetent. We need to build more safety margins into systems mainly for wear, not chase mongoloid-strength 80ksi cartridges.

 

[putput30]

I’m still waiting for a 25 caliber intermediate cartridge to come out. 25 cal should be the ideal balance of bc, sd, energy and recoil. If they can get that out of the ar15 with a redesigned bolt and extension even better.

 

[Cascade Hemi]

Do you have no concept of burn speed and pressure curve shape? I pulled 2600 as a rough number off the chart above, but the Hornady manual lists two loads that have a 108 going 2575 out of an 18" at max.

I've been handloading these cartridges for a long time and I've chronographed thousands of rounds of Grendel. Your post is bullshit.

Cartridge : 6 mm ARC
Bullet : .243, 108, Hornady ELD-M 24561
Useable Case Capaci: 29.273 grain H2O = 1.901 cm³
Cartridge O.A.L. L6: 2.260 inch = 57.40 mm
Barrel Length : 18.0 inch = 457.2 mm
Powder : Hodgdon LVR

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-10.0 97 26.10 2261 1226 39142 9243 90.0 1.187
-09.0 98 26.39 2288 1256 40470 9375 90.6 1.168
-08.0 99 26.68 2316 1286 41846 9504 91.2 1.149
-07.0 100 26.97 2343 1316 43274 9631 91.8 1.131
-06.0 101 27.26 2370 1347 44756 9755 92.3 1.114 ! Near Maximum !
-05.0 102 27.55 2398 1379 46292 9876 92.9 1.096 ! Near Maximum !
-04.0 103 27.84 2426 1411 47890 9995 93.4 1.079 ! Near Maximum !
-03.0 104 28.13 2453 1443 49549 10111 93.9 1.062 ! Near Maximum !
-02.0 105 28.42 2481 1476 51270 10223 94.4 1.046 ! Near Maximum !
-01.0 106 28.71 2509 1509 53062 10333 94.9 1.029 !DANGEROUS LOAD-DO NOT USE!
+00.0 107 29.00 2537 1543 54924 10439 95.3 1.013 !DANGEROUS LOAD-DO NOT USE!
+01.0 109 29.29 2565 1577 56861 10541 95.8 0.998 !DANGEROUS LOAD-DO NOT USE!
+02.0 110 29.58 2592 1612 58875 10640 96.2 0.982 !DANGEROUS LOAD-DO NOT USE!
+03.0 111 29.87 2621 1647 60974 10735 96.6 0.967 !DANGEROUS LOAD-DO NOT USE!
+04.0 112 30.16 2649 1682 63160 10826 96.9 0.952 !DANGEROUS LOAD-DO NOT USE!
+05.0 113 30.45 2677 1718 65431 10913 97.3 0.937 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 107 29.00 2678 1720 66717 10502 99.4 0.935 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 107 29.00 2356 1331 44636 9828 87.2 1.113 ! Near Maximum !

 

[LRRPF52]

Don't spew easily disproven nonsense:
View attachment 8536320

Values pulled directly from 4DOF (STP, 10mph crosswind)
View attachment 8536321

It wasn’t on Hornady’s desktop program. I just checked it to see if they had added the 100gr ELD-VT and it still isn’t there. It is on the Hornady phone app though.

Don’t assume malice. That 4DOF program does match my 1k drop dead-on though. I was holding less wind.

I’ve been using G7 for the 100gr ELD-VT in the absence of the 4DOF. Those are different results for sure.

If the data shows I’m wrong, I’ll own it. It didn’t make sense to me either because the BC advantages are clearly in 6mm favor until you step up in weight with 6.5mm, but then trajectory gets more 175gr SMK-like.