Testing, testing...

[Tony Williams]

I think this is a very good approach. However, I see a couple of problems to "firming up on the required calibre and ballistics."

1. There is no consensus as to whether:

• Only 5.56x45 should be replaced.
  
• Only 7.62x51 should be replaced.
  
• Both 5.56x45 and 7.62x51 should be replaced.
  

Replacing only 5.56x45 with a bigger, heavier cartridge (like 6.5 Grendel and 6.8 SPC) increases the rifleman's carry load and/or decreases the number of rounds he carries, but does not change the machine gunner's load.

Relacing only 7.62x51 with a smaller, lighter cartridge (like 6.5x45 and 7x46) decreases the machine gunner's carry load and/or increases the number of rounds he carries, but it slightly increases the rifleman's load (if he is tasked to carry extra ammo for the machine gun).

Replacing both 5.56x45 and 7.62x51 with a single, intermediate cartridge (like 6.5x45 and 7x46) decreases the machine gunner's carry load and/or increases the number of rounds he carries, but it also substantially increases the rifleman's load (especially if he is tasked to carry extra ammo for the machine gun) and/or decreases the number of rounds he carries.

Then there is the (so far undiscussed) idea of replacing 5.56x45 with a bigger, heavier cartridge (but one not as big or heavy as 6.5 Grendel and 6.8 SPC), and replacing 7.62x51 with a smaller, lighter cartridge. This would impose less penalties on the rifleman than would a "unified" caliber.

I don't see much prospect of a new round just to replace 5.56mm. The counter-argument will always be that 5.56mm is normally good enough (especially given M855A1 or MK318) and for circumstances in which it isn't good enough, there are 7.62mm weapons available.

Replacing the 7.62mm with a lighter round of equivalent long-range performance is likely to be more attractive to the army (US or UK) since they are very concerned about reducing the huge burden carried by dismounted troops. I may be wrong, but I get the distinct impression that with the return of 7.62mm rifles and LMGs to section level (which seem to have greatly impressed troops with their range and hitting power), 5.56mm is increasingly seen as a short-range carbine calibre which may not have much of a future in belt-fed LMGs. In which case, adopting a lighter replacement for the 7.62mm would reduce the load of infantrymen carrying ammo belts, not increase it.

By definition, a lighter, smaller-calibre long-range round to replace 7.62mm would also generate less recoil. Having tried HK 416 in 5.56mm and 6.8mm plus HK 417, all in quick succession, I found that the perceived (as opposed to calculated) recoil of the 6.8mm was much closer to the 5.56mm than to the 7.62mm. This makes a long-range intermediate round of similar power a realistic proposition for replacing 5.56mm in rifles and carbines. Yes, there would be some penalty in ammo weight (or alternatively the infantryman would carry fewer rounds) but the greater range and effectiveness of the ammo might well trump that. Especially given the work on advanced sighting systems which will make hitting targets at long range much easier. And, perhaps of the greatest appeal to the bean-counters, a unified calibre should save money - in halving the number of weapon types to be acquired, maintained and trained for.

2. There seems to be almost no publicly available test data on terminal effects of "eco-friendly" military ball projectiles. Without such data, how can we possibly make a logical, rational decision as to which caliber is optimum?

All I've seen are assurances that the M855A1 and the British 5.56mm HP produce more consistent terminal effects, but no evidence in support. But ARDEC did all the testing in different calibres using military-style green bullets and concluded that 6.8mm was best...