Testing, testing...

[stanc]

If we were considering lead-cored bullets then I would definitely go for 6.5mm. With non-lead bullets it may be that a larger calibre is needed to get a reasonable weight.

I got to thinking (Which is always dangerous! ) about that. Did a rough sketch of a 6.5mm "EPR" projectile, modifying the 120gr GMX with an M855A1-type penetrator. (See attached.) I don't know how to make a close estimate of what the bullet weight would be reduced to by using steel where higher-density gilding metal was previously, but it would almost certainly weigh less than 120 grains, perhaps 115 or so?

Note that, compared to M855A1, the 6.5mm penetrator is much longer relative to bullet length, and the base slug is much shorter. Also, at 1.403" length, the base of the 6.5mm bullet will extend rather deep into the cartridge case, reducing the powder volume. The solution would seem to be shortening the tail end of the projectile, and thereby increase powder space.

However, shortening the bullet's rear will further reduce weight, to maybe 105 grains? That would also reduce the BC, possibly impacting trajectory and retained velocity/energy. But, it'd enable MV to increase, which is good. A bad point is that this shortening would shift the center of balance forward, which would likely delay yawing in soft tissue.

I haven't done a similar drawing for 6.8mm and 7mm, but going by this one, it looks as if you may be right about a "green" 6.5mm bullet not being heavy enough. Thoughts?