06-08-2022, 12:38 AM
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
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:
www.AR15buildbox.com
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com