Denfoote
"You know that shoot around the corner rifle was developed a few years back, as I recall. I don't think it works very well. As far as I know, nobody uses it!!"
Lots of people use it, the developers refuse to sell to anything other than gov't agencies though. I believe even the US Marines use them, and have seen combat, in executive protection areas. AIUI they ducked behind cars and held the guns up to shoot over.
HUWS, it seems to me that the problem with airburst ammunitions would be laser range-finders , the same problem as with early image-intensifiers, they're active. While not popular in western tanks, you should know that Chinese and others have laser-detectors built into their vehicles. The Chinese and the Russians have systems to detect and respond to being illuminated by lasers (enemy tank's range-finders). The Russian system slews the turret towards the laser and releases smoke, the Chinese system can even reply with a dazzling laser of its own.
A few questions I'd have to wonder about would be:
1)How great is the dispersion of the laser at useful ranges, how easy is it to detect, could it be aimed precisely enough to avoid tripping the theoretical laser detector?
2)How could one target things like trenches or holes in the ground? If objects nearby were targeted, would there be laser 'splash' off of them that would trip laser detectors?
3)Wouldn't a larger payload than 20mm offers be much preferable for airbursting projectiles?
And one point - as I understand the theory to work, if a 20mm were to airburst near you, it would be very near to you. As such I'd have to guess that multiple projectiles would hit you, and would cause a lot of disturbance. Even ballistic eyewear wouldn't be rated against this threat.
Further point, have you looked at the Singapore or Israeli airbursting weapons? They're based on a simpler sytem, all ready for use, and have a 40mm warhead.