New Army "Caliber Configuration Study"

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A comment on bullet design: it does not necessarily follow that a lengthened bullet has a better Form Factor, if the extra length just goes into the shank, leaving the nose and tail profiles the same.

This can be demonstrated by comparing the 7.62mm M80 with the M118 sniper loading (both lead-cored). The M118's FF is almost exactly the same; it has a better BC simply because it's heavier.

Thanks for that info, Tony. I would note that the M118 Match bullet has a tangent ogive, whereas that of M80 Ball is secant. A better comparison would be to steel-core M59 Ball (left, below), which also has a secant ogive, and weighs approximately the same as lead-core M80 Ball (right, below). Do you happen to know the FF of the M59 bullet?

Extra length can permit a better FF by allowing a longer, more tapered ogive - but only if the COAL permits this.

The US has a long tradition of designing cartridges with COALs too short to permit the use of high-BC bullets with long ogives. The 6.8mm Rem is perhaps the most extreme recent example of this...

One of the key design points of any new military cartridge should be that the specification must allow the use of long-ogive bullets, since they can provide a significant improvement in long-range performance without any extra power, weight or recoil.

I wholeheartedly agree. We can only hope the military will, too.

Apart from slightly longer gun actions and magazines, it provides extra performance at no cost.

Yes. It causes me to wonder how much performance would improve by simply increasing cartridge OAL of 5.56 and 7.62 NATO.

On your MG&A forum, Badcow454 stated that the 7.62x51 case loaded with a scaled-up 7N6 bullet would have a 2.94" COAL. Since the FN MAG was originally adopted by Sweden in 6.5x55, which has a 3.15" COAL, it would seem a relatively easy task to adapt MAG variants to use 7.62x51 with long-ogive bullets.

Of course, this concept could also be applied to 6.8 SPC, as well as variations like 6.5 SPC.

Question: What do you get if you scale up the 5.45x39 round by a factor of 1.1?
Answer: A long-loaded 6mm SPC.