04-07-2014, 08:13 PM
As I understand it, the 6.5x40 was specifically designed to replace the 5.56x45. Even if the listed performance is a bit optimistic, it does a pretty good job at that. Notice, however, that all three of its loadings are in or near the transonic region at 600m and all are subsonic by 800. Many bullets lose accuracy in the transonic region and become less useful for aimed fire.
As LRRPF52 pointed out, more powder volume is needed to get the desired performance and keep pressures down.
The 6.5 Grendel is much closer to a General Purpose Cartridge (GPC), one which would replace the 5.56x45 AND the 7.62x51 for infantry. When using the Lapua 123, the ballistics are pretty much there.
Unfortunately, the military seems to want lead-free bullets. A bullet made of steel, brass, or a mixture of both will be less dense, so its ballistics coefficient will be lower than a similar shaped copper/lead one. Also, polymer cases are on the horizon. So far, the wall thickness for polymer cased is thicker than brass, meaning less powder. There will also need to be a tracer version.
Now I have bumbled into topics being discussed in the Military & Law enforcement threads, so I will stop.
As LRRPF52 pointed out, more powder volume is needed to get the desired performance and keep pressures down.
The 6.5 Grendel is much closer to a General Purpose Cartridge (GPC), one which would replace the 5.56x45 AND the 7.62x51 for infantry. When using the Lapua 123, the ballistics are pretty much there.
Unfortunately, the military seems to want lead-free bullets. A bullet made of steel, brass, or a mixture of both will be less dense, so its ballistics coefficient will be lower than a similar shaped copper/lead one. Also, polymer cases are on the horizon. So far, the wall thickness for polymer cased is thicker than brass, meaning less powder. There will also need to be a tracer version.
Now I have bumbled into topics being discussed in the Military & Law enforcement threads, so I will stop.