05-17-2011, 02:22 AM
One thing I want to point out, which many of you already know from looking at your bullet boxes, is that 6.5mm projectiles that are .264" are really 6.71mm, not like the real 6.5mm or .257". To see the difference between a 7mm, 6.8mm, and 6.71mm requires me to use calipers. I do realize that bullet weight can be increased slightly with the 7mm, but we're basically in the same ballpark. I see a slightly shorter cartridge than 7.62 NATO working well, but it really doesn't matter too much for the belt-fed weapons and existing SASS systems.
I also have some ideas for propellant design changes that are radical, but still use existing metallic cases until the next generation of solid or telescoped cases mature, if they are not skipped by magnetic rail guns, man-portable lasers, or microwave weapons. The improved propellant could theoretically make the Grendel case capable of what a 6.5x47 Lapua does now, but I don't have a degree in chemistry, nor do I have access to the R&D facilities at DuPont.
I would still like to see a muzzle velocity of at least 2800 fps versus 2600 fps for the LMG ammunition. When I ran my .260 AR10 with 130 Bergers in a running-gun stage at FinnSniper last year, it was really pleasant to shoot off-hand on IPSC targets wearing Russian uniform tops that were at CQB distances, and I had almost all "A"s on them using a S&B PMII on 3 or 4x. I have learned that .260 Rem has way too much case capacity for long .264" bullets loaded even to mag length, but I would also prefer a cartridge with a smaller head diameter for space efficiency for Joe to hump around.
There are a lot of good points made by the various enthusiasts and professionals in the firearms community right now, however, I do see listings for G1 Ballistic Coefficients for longer, sleeker bullets pushed at moderate velocities and then chart comparisons against 7.62 NATO. I don't know if the G1 figures are used across the board for all the cartridges, but I and many other long-range shooters have found G1 BC data to be inferior to G7 data when looking at distances past 300m, which is where BC starts to come into play. The main conclusion the super nerds with higher math backgrounds have come to is that radar data, then G7 data are the way to go, and that BC increases with velocity.
The threshold I would want would be a muzzle velocity of 2800fps with at least a 6.71mm projectile with a G7 BC above .215, which leans more towards 130gr bullets. M80 ball has a G7 of .198, so that is what would have to be beat by the new cartridge in mass-produced form. I lean more towards MV than expensive bullet shaping for a belt-fed gun, since cost-effectiveness for belt-fed projectiles needs to come into play. The longer 6.71-7mm projectiles will facilitate tracer use since they are long already.
The most important things are reducing weight for the guns, and getting a lighter-recoiling cartridge, with a little gain in trajectory advantage. The calibers we're talking about seem capable of doing that right now, with FMJ's or acceptable mass-produced ammo per current guidelines.
LRRPF52
I also have some ideas for propellant design changes that are radical, but still use existing metallic cases until the next generation of solid or telescoped cases mature, if they are not skipped by magnetic rail guns, man-portable lasers, or microwave weapons. The improved propellant could theoretically make the Grendel case capable of what a 6.5x47 Lapua does now, but I don't have a degree in chemistry, nor do I have access to the R&D facilities at DuPont.
I would still like to see a muzzle velocity of at least 2800 fps versus 2600 fps for the LMG ammunition. When I ran my .260 AR10 with 130 Bergers in a running-gun stage at FinnSniper last year, it was really pleasant to shoot off-hand on IPSC targets wearing Russian uniform tops that were at CQB distances, and I had almost all "A"s on them using a S&B PMII on 3 or 4x. I have learned that .260 Rem has way too much case capacity for long .264" bullets loaded even to mag length, but I would also prefer a cartridge with a smaller head diameter for space efficiency for Joe to hump around.
There are a lot of good points made by the various enthusiasts and professionals in the firearms community right now, however, I do see listings for G1 Ballistic Coefficients for longer, sleeker bullets pushed at moderate velocities and then chart comparisons against 7.62 NATO. I don't know if the G1 figures are used across the board for all the cartridges, but I and many other long-range shooters have found G1 BC data to be inferior to G7 data when looking at distances past 300m, which is where BC starts to come into play. The main conclusion the super nerds with higher math backgrounds have come to is that radar data, then G7 data are the way to go, and that BC increases with velocity.
The threshold I would want would be a muzzle velocity of 2800fps with at least a 6.71mm projectile with a G7 BC above .215, which leans more towards 130gr bullets. M80 ball has a G7 of .198, so that is what would have to be beat by the new cartridge in mass-produced form. I lean more towards MV than expensive bullet shaping for a belt-fed gun, since cost-effectiveness for belt-fed projectiles needs to come into play. The longer 6.71-7mm projectiles will facilitate tracer use since they are long already.
The most important things are reducing weight for the guns, and getting a lighter-recoiling cartridge, with a little gain in trajectory advantage. The calibers we're talking about seem capable of doing that right now, with FMJ's or acceptable mass-produced ammo per current guidelines.
LRRPF52