Testing, testing...

[stanc]

...the situation continues to evolve. The widespread distribution of 7.62mm rifles and MGs down to section level (helped by the fact that the British have just joined the US in selecting the 7.62mm Minimi) has to a large degree addressed the range and (to some extent) the effectiveness issues of 5.56mm, but has created a new problem - ammo weight!

I see. Back to the future. Seems we've (partially) returned to the 1950s in that regard. Kinda funny, actually.

I wouldn't argue with that: my suggested ideal cartridge in calibres between 6.5mm and 7mm is based on the 6.8 Rem case, but slightly longer, and with space for a much longer bullet. In terms of conventional ammunition technology, I think this could represent the ideal dimensions and proportions.

It might. One advantage to the 43mm SPC case is that it can be loaded to OAL of 2.25" for conversion of 5.56x45 weapons, or to OAL of 2.40-2.50" for use in a new platform.

If we were sticking to lead+steel cored bullets I would choose 6.5mm as the ideal calibre, but with copper+steel (or even just steel) bullets as seems mandatory nowadays, getting sufficient weight within a reasonable length becomes a problem for long, VLD bullets.

I agree. Almost everybody is still looking at lead-core bullets, when they should be doing "green" projectiles. I've been guilty of this myself, even after pointing out a year or two ago that bullets for alternative calibers should be (in the USA, anyway) of the M855A1/M80A1 type.

Bill Alexander was apparently paying attention, though, as he's trying to get a T3 bullet made for 6.5 Grendel. I can't help wondering how heavy a 6.5 T3 can be, without becoming too long. My calculations (which may be faulty) say that scaling down the 130gr M80A1 would be a mere 82gr in 6.5mm, and 149gr M80A1-A, only 94gr. That would certainly boost muzzle velocity, but downrange velocity would suffer significantly.

Then there is the question of terminal effects with the necessarily long, eco-friendly projectiles. Will they be capable of early yaw in flesh? Photos of M855A1 into bare gel, which would shed some light on that question, have yet to surface.

We may be able to get away with being close enough to M80 performance for the difference not to be significant, rather than exactly matching it. However, if the long-range performance falls noticeably short then the new round won't be able to replace 7.62mm and the argument for it will thereby be substantially weakened IMO.

Concur.