Grendel as a Universal Infantry Cartridge

[stanc]

The problem with designing the cartridge to achieve a given performance from a 14" barrel is that it will need to be more powerful than one which achieves the same performance from a 20" barrel. So the cartridge will be bigger, heavier, recoil more and produce a lot much more muzzle flash and blast - which are all undesirable.

To be sure.

On the other hand, if you accept that you're only going to achieve the long-range performance you want from a 20 inch barrel so will only be able to use MGs and DMRs at long range then you can use the smaller cartridge, but the short-barrelled carbine will then be limited in its range performance. So you will still have two shoulder guns - a long-range rifle and a shorter-ranged carbine - instead of one general-purpose one, although the difference in their performance will be nowhere near as great as it currently is between 5.56mm carbines and 7.62mm rifles.

Must we accept that a 20" barrel is needed? Wasn't the L129A1 (which has a 16" barrel) adopted for the long-range requirement?

I'm thinking that it'd be possible to develop a long range cartridge better than 7.62 NATO for 16" barrel weapons. More importantly, it seems like it'd be far easier to get a 16" carbine adopted by the US Army than a 20" bullpup rifle. Maybe easier to get adopted by the British Army, too, if they've soured on bullpups.