04-18-2012, 02:41 AM
A 43mm case + long ogive projectile will have a depth volume longer than a 39mm case though. No matter what projectile diameter is selected, trying to invent a new case from scratch will probably invoke at least 2 existing parent cases that have already existed for 50-70 years. The 7mm UIC uses 6.5 Carcano case head dimensions, the 6.5 Grendel has a family tree with the great grandfather being the 7.62x39, and the 6.8 SPC has the .30 Remington as its parent-a cartridge introduced more than 100 years ago in 1906.
We know that 6.5mm projectiles are the optimum, most efficient bullet for retained energy and penetration at distance from short-action cartridges and rifle/MG platforms. Those are traits that serve a GPMG and DMR well, but not a carbine meant for closer range work.
For cases, we are seeing that .421"-.445" case heads are being zeroed-in on in an attempt to reduce load volume and weight from the 7.62 NATO and its .473" case head. There isn't a real need to develop a new case when you already have one that is capable of 62,000 psi, has a .445" head, and is only 39mm long, leaving the ability to load long-ogive projectiles that are ideal for distance work. We're about maxed out on compactness and performance at the intersection of the Grendel for a metallic ammunition cartridge to be used in a smaller action.
We know that 6.5mm projectiles are the optimum, most efficient bullet for retained energy and penetration at distance from short-action cartridges and rifle/MG platforms. Those are traits that serve a GPMG and DMR well, but not a carbine meant for closer range work.
For cases, we are seeing that .421"-.445" case heads are being zeroed-in on in an attempt to reduce load volume and weight from the 7.62 NATO and its .473" case head. There isn't a real need to develop a new case when you already have one that is capable of 62,000 psi, has a .445" head, and is only 39mm long, leaving the ability to load long-ogive projectiles that are ideal for distance work. We're about maxed out on compactness and performance at the intersection of the Grendel for a metallic ammunition cartridge to be used in a smaller action.