07-06-2011, 07:04 PM
stanc Wrote:...Diameter of 0.44" and length of 2.8" is, IMO, much too close to the 0.47" / 2.8" of 7.62x51...This is Grendel-class diameter - same as 7.62X39 and the 6.5x45 Czech within a 2-3 thousandths of an inch. Going down to say, the .422" of the 6.8 SPC / .25 Remington reduces the powder capacity a bit much, even if the COAL is the 2.80" allowable within the 7.62X51 envelope.
We will need this powder capacity to get adequate muzzle velocity -- especially if it becomes clear that the 7mm is the minimum caliber.
Even so, we will be challenged to show that a 6-8 gram bullet of any caliber can be as effective as the 9.5 gram M80 round -- this in spite of reasonably sure knowledge that these are highly capable bullet weights in the calibers we're discussing.