gatnerd said:

Would it be for improving the ability to set cars/technicals on fire over current .50? And is the current .50 lacking in that regard? Or would the payload offer some other benefit, such as improving the ability to shatter/smash through walls and concrete? 

Today, most APCs are already immune to 14.5x114 mm AP rounds on the frontal and lateral arc, so I don't think trying to increase the AP capability of a .50" is the way to go.

The .50'' SLAP is already existing, fielded and delivering 14.5 mm AP performance, but only the USMC is using it, and in limited numbers.

The .50" MP, on the other hand, is used by nearly every western armies, and gives decent AP capability + 1 g of HE payload and fragments. Those fragments are not going to penetrate any armor but are great to defeat cameras, sensors, antennas, RWS... located on every current APC, and also to effectively defeat "technicals" or suicide bomb cars.

The current way to "upgrade" the M2HB is to replace it with a 40 mm "High Velocity" grenade launcher, so a truly "high velocity" round that retain the external ballistics of the .50 BMG, but with a bigger payload (the .61" vs. .51" is a ~20% increase of the diameter and ~70% increase of the volume) may be the way to go (or the diameter should be increased to ~18 mm to carry enough HE to justify the upgrade, like the experimental 18x81 mm Tarantula).

The problem with the 14.5 mm / 20x102 mm / 30x113 mm upgrade is that those 3 rounds are using twice the propellant load of the .50" BMG, you simply can't expect to replace a M2HB with those without any side-effect.

for a 50 replacement, what are you thoughts on a higher powered round which is designed around a very potent Apfsds round. (all of it's ammo options are telescoped including API)

lets say the muzzle energy was 20k Ft Lbs....would the dart be much use against vehicles in realistic scenarios?

Why not just do this?

Yes, a full auto version of the IWS. 

Seriously though, wouldnt an APFSDS with 20k ft lbs be more destructive than an API round?

I came across this truly superb article on the effectiveness of a 20mm AMR. 

Worth checking out. Theres penetration fragmentation data, long range ballistics, recoil impulse data, surveys of current off the shelf systems, and potential design features of a future AMR rifle:

https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2009/infantrysmallarms/thursdaysessionxi8503.pdf

Theres 48 pages of great data in there, but the conclusion is:

Yes, that is an excellent presentation.

Regrettably, little appears to have progressed in the 12 years since I first read the article.

I’d like to see a 20mm AMR broadly adopted, not limited to SOF. Infantry and engineer platoons could benefit from the capability.

I would opine that the lack of progress is due to a 20m AMR being too much of a niche weapon, even for special forces.

For infantry platoons, a multi-purpose weapon makes far more sense, hence the USMC and Army choosing the M4 CG.

YouTube

Why the M4 Carl Gustaf is so deadly

Saab's new Carl Gustaf, the M4 or M3E1, is roughly 6.5 lbs lighter but is smarter and far more lethal than its predecessor.More Information: https://www.mari...

Lynx looks exciting but honestly many 50BMGs i shot were rather soft on recoil due to massively effective muzzle brakes so i am kinda skeptical that this is cutting the recoil much. And its also designed as short range anti material rifle with sub 1000m practical range.

https://www.youtube.com/watch?v=FDfLKpOkWVg

YouTube

GM6 Lynx Semi Auto 50 BMG Bullpup 4K UHD

12,7x99 (.50 BMG)GM6 Lynx is a revolutionary, unique new weapon combining light weight with portability, mobility and heavy fire power.FEATURESMost advance A...

I actually like the gm6 and the niche it puts itself in.

For something like a vehicle checkpoint where you may need to stop a vbied coming at you, you don't actually need more than 1k meter range as much as you need the ability to pump multiple raufoss or m8 API into something QUICKLY.

By being shorter and easier to fire quickly it does this better than other options. You can conceivably hoist this over a jersey barrier get behind it and pump rounds quickly then move if necessary.

Maybe there's something I fundamentally misunderstand here but I can appreciate the tradeoffs they're making, including the >1k meter precision sacrifice.

Put bluntly in many cases the guy nearest this gun at the time it needs to get used probably doesn't really know how to shoot past 1k effectively anyway.

I know I certainly don't have the skills necessary to do that truly well.

To a degree I think it's a weapon good for the force and enablers we have rather than the Ultimate tool for the ideal paper force that has nothing but guys trained to shoot past 1k effectively and $30,000 high end enablers like 3rd gen flir fuzed night vision and thermal optics etc that can identify and resolve a target sufficient to make it within ROE to be permissible to shoot.