Tested 4 Calibers: .30 .27 .24 and .21 and 3 powder loads 100%, 80%, 60% of a 30-06 cartridge.
The Charts shows the positive results moving from the 30-06 cartridge to .224 caliber for 400 yard combat with only 60% gun powder. Both better Hit Probability and Wounding Power.
The Charts shows the positive results moving from the 30-06 cartridge to .277 Fury at all combat ranges, they had to increase the pressure to get 30-06 performance out of a 308 size case with a short barrel. Both better Hit Probability and Wounding Power at all ranges.
A 6.5 Grendel like load was in the study but it did poorly relative to 30-06 cartridge. This may be why 6.5 Grendel and 6.8 SPC ammo never was a final solution to the US military. The lowest line on both charts was like AK 47 like cartridge.
I marked the charts with load similar to .277 Fury, 270 Win, .25-06 Rem, 30-06, .224 Valkyrie, and 6.5 Grendel.
Tested 4 Calibers: .30 .27 .24 and .21 and 3 powder loads 100%, 80%, 60% of a 30-06 cartridge.
The Charts shows the positive results moving from the 30-06 cartridge to .224 caliber for 400 yard combat with only 60% gun powder. Both better Hit Probability and Wounding Power.
The Charts shows the positive results moving from the 30-06 cartridge to .277 Fury at all combat ranges, they had to increase the pressure to get 30-06 performance out of a 308 size case with a short barrel. Both better Hit Probability and Wounding Power at all ranges.
A 6.5 Grendel like load was in the study but it did poorly relative to 30-06 cartridge. This may be why 6.5 Grendel and 6.8 SPC ammo never was a final solution to the US military. The lowest line on both charts was like AK 47 like cartridge.
I marked the charts with load similar to .277 Fury, 270 Win, .25-06 Rem, 30-06, .224 Valkyrie, and 6.5 Grendel.
danm Wrote:Nice work! Wonder why the 6ARC was adopted by some special units considering this chart???
Technology has changed the assumptions made in these earlier studies. They were based on iron sights and old models of "wounding power". The introduction states: "For the purposes of the study, Hall discounted any effects of gyroscopic instability that induced tumbling or fragmentation." Tumbling (yaw) and fragmentation are now known to extremely important in terminal effects, so this data grossly underestimates the wounding potential from US 5.56x45 ammo at fragmentation ranges, for example. These calculations are highly biased on high velocity generating short flight time, flat trajectory and high kinetic energy. The idea of each soldier having a clear magnified optic and the ability to accurately determine the range was Buck Rodgers science fiction at the time.
The interest into 6ARC has more to do with experience in Afghanistan, improved optics and bullet design. Studies from WWII and Korea indicated that roughly 90% of all fighting occurred at distances less than 300 yards. There are some videos online in which Eugene Stoner stated that infantry did not need a rifle with capability for combat beyond 300m. In the past decade or so however, we began to see reports along the lines of ""U.S. Army data....reveals that more than half of the wars small arms engagements are now beyond 500 meters" (American Rifleman, Feb 2011). My guess is that the 6mm ARC was developed to meet some spec of a certain amount of energy at some long distance like 800 or 1000m. It may well have a dual spec for DMR use with high-BC lead-core ammo and a lesser one for Steel/brass EPR-style bullets. The EPR will have better behind-barrier effect but a lower BC because brass and steel are less dense than lead. As for why 6mm instead of 6.5mm Grendel, it probably has do do with what was closer to the specification.
In some respects, whereas the 6.8 NGSW was intended to improve upon the performance of 7.62x51 with increased ability to penetrate body armor as well as increased accuracy and effect at long ranges, the 6mm ARC is intended to do the same thing for the 5.56x45.
Fess Wrote:Technology has changed the assumptions made in these earlier studies. They were based on iron sights and old models of "wounding power". The introduction states: "For the purposes of the study, Hall discounted any effects of gyroscopic instability that induced tumbling or fragmentation."
I remember reading a test from WW2 era. Author noted that a .30-06 could NOT penetrate 12 inches of oak at 50 yards, but at 200 yards it could penetrate about 36". At the time, they considered this kind of penetration a good thing.
They first looked at 6.5 Grendel as the most obvious solution to their problem, but developed 6ARC because it had better external ballistics than 6.5 Grendel.
It is also claimed in Hornady's YouTube podcast at 15:14 HERE that the 6ARC has BETTER wound ballistics than 7.62x51.
:: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets
There was no 6.5 Grendel or .224 Valkyrie mentioned in any of those tests, as neither existed in 1950. Closest thing to 6.5 Grendel in 1950 would have been 6.5x54 Mannlicher-Shoenauer, though not in external ballistics. 6.5 M-S shot mostly round-nose late 1800s style projectiles.
The main conclusion from Halls 1950-1952 study was that if you propel a 60gr .224 bullet along at 3660fps, it has a higher hit probability and wounding potential than .30 Cal M2 (.30-06).
You would need a cartridge that holds 40.5gr of propellant, with a long barrel to achieve those velocities at the time.
If you follow the timeline of SCHV development, they went from that 3600fps mv goal, down to 3500fps, then to 3400fps, then 3300fps, which is about where M193 landed with a 55gr FMJBT fired from a 20 barrel. The 22 barrels would give you 3300-3360fps, but needed to be pushed to the edge in terms of acceptable MAP, pushing over that too often for production considerations.
After the AR-15 was ordered by the USAF, circumventing Army Ordnances attempts to sabotage and derail it, one of the Army Ordnance engineers proposed taking the .25 Remington cartridge and necking it down to .224 to meet the higher mv requirement, but proponents of the AR-15 felt that this would suck the momentum from their project because the receiver set, Bolt Carrier Group, barrel extension, and magazine would all need to be re-designed to be slightly larger. That would have made the rifle and cartridge system far more versatile in the long run, especially for 6mm, .257, and 6.5mm, as the magazine well would have facilitated a 2.500 COL.
With SCHV, they were trying to muscle towards various terminal performance objectives with brute force in mv, and had some understanding of BC, but didnt focus on it enough. The thinking was that MV helps with Time of Flight, which helps with shooting moving targets. The last time I ran the numbers for ToF, there werent noticeable differences between several production cartridges within 200yds, as the high BC samples hit the same ToF due to efficiency. Were talking .25 seconds being common for all of the ones I ran the ballistics on, with small deviation in the 2nd decimal place. If you use the 3600fps mv, you can get the ToF down to sub .2 second speeds.
Interestingly, the 6.5 Grendel is very similar to M2 .30 Cal in external ballistics if you look at the 173gr FMJBT compared to 123gr HPBT.
Another major observation from their studies was that shot dispersion increased hit probability, which launched Project SALVO. SALVO had all sorts of proposals, including duplex cartridges, dual-barrel rifles, flechettes, burst firing mechanisms, and underslung grenade launchers.
The M16A2s 3rd BURST mechanism is a watered-down, ill-executed fire control group that made its way into the rifle.
The main useful performance areas they were trying to accomplish were:
High MV for short ToF
Low Recoil
High shot concentration from multiple shots into a short time duration to increase hit probability
High ammunition carrying count
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
Weren't the Germans trying to solve the "fleeting target" problem with the high cyclic rate of MG34 and MG42?
Fleeting target issue is a thing. In "With the Old Breed: At Peleliu and Okinawa" Sledge tells the story on Okinawa they had to run back and forth from one mound to another, and every time they were briefly exposed in the gap a Japanese machine gun opened up on them, and it was causing problems. They solved it by parking a Sherman in the gap for cover and ran behind it.
Pretty sure the increased recoil of 6.8 NGSW is not gonna help the fleeting target problem despite fancy sights. Maybe you only get one shot before recovering your sight picture while a milder cartridge gets three? Don't know....
:: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets
MGs had high cyclic rate, while the Sturmgewehr had really low cyclic rate.
FG42 also had low cyclic rate, which is why the M60 had low cyclic rate. M60 is an FG42 with MG42 feed tray mechanism and cover basically.
With MP44 Sturmgewehr on automatic mode, you can maintain really nice rate of fire on-target on runners within short distances because it has low cyclic rate and constant recoil operating principle.
You can easily break single shots on automatic mode too since the cyclic is so slow.
Jim Sullivan developed some different components to try to make the AR-15 more like that, with the Rate Reducing Buffer, but I like the normal cyclic rate on semi in the AR since recovery is quite easy for a trained shooter.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
Tested 4 Calibers: .30 .27 .24 and .21 and 3 powder loads 100%, 80%, 60% of a 30-06 cartridge.
.30 with 100% Powder is like a 30-06
.27 with 100% Powder is like a 270 Win or 277 Fury
.24 with 100% Powder is like a 25-08 Rem
.21 with 100% Wildcat 22-08
.30 with 80% Powder is like a 308
.27 with 80% Powder is like a 6.5 Creedmore
.24 with 80% Powder is like a 243 Win
.21 with 80% Powder is like a .22-250 Remington
.30 with 60% powder is like a AK 47
.27 with 60% powder is like a 6.5 Grendel
.24 with 60% powder is like a 6mm ARC
.21 with 60% powder is like a 244 Valkyrie
LR, so it sounds like the "fleeting target" thing is not a thing anybody's tried to solve with technology. If high cyclic rates were the solution, you'd think everybody would have done it.
:: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets
It is not uncommon to get only one shot at a fleeting target. That is why high velocity and short flight time tend to do better in those tests. Features planned for a future iteration of the wonder-optic involve identifying the target and sending the round downrange only when the fire-control-system says it will hit. There has also been considerable work done on chassis systems that will slightly yaw the barrel as the trigger is pulled to assure a hit. I am not at all certain that the barrel-yaw system will ever get light and compact enough to work in a general purpose firearm, though.
