06-10-2012, 05:19 AM
Tony Williams Wrote:...the case width limits the maximum safe pressure to around 50,000 psi, which I suspect isn't quite enough to extract the performance required to replace the 7.62mm. Particularly when the US Army's preference for lead-free bullets is taken into account (longer bullets = less room for propellant). So all of the proposals below exceed the overall length of the 5.56x45...I like the photos!
There seems to be continuing confusion, however, about the pressure limitations of the Grendel cartridge.
Per Bill Alexander, the base width indeed places more thrust on the AR15 bolt, which results in reduced average bolt life when run at pressures significantly above 50,000 psi. This is a reliability issue unique to the AR15 bolt.
Also, Bill indicates that Grendel case itself can readily handle upwards of 58000 psi.
These pressures are safe in appropriate actions. When coupled with a longer COAL as suggested, then the desired velocities and bullet weights for supplanting the 7.62X51 M80 cartridge are likely attainable.