"Meanwhile, current 40x46 already has pretty marginal lethality, so it's hard to see them going to a much lighter grenade."

I've wondered why the U.S. uses the HEDP but not a dedicated HE projectile in both their 40 X 46 and 40 X 53 grenade launchers.

A well designed HE would have a better lethally radius. With airburst fuse or bounding ammunition it would be even better.

17thfabn said:

I've wondered why the U.S. uses the HEDP but not a dedicated HE projectile in both their 40 X 46 and 40 X 53 grenade launchers.

HEDP was opted for in order to have one ammo type that could be used against both personnel and light armored vehicles.

HE is ineffective against light armor, so grenadiers would have to carry reduced amounts of two ammo types:  HE and HEAT.

taschoene said:

I'm trying to imagine alternative approaches that could be applied.  Maybe a 40mm GL-compatible course-corrected rocket for the counter-defilade round to get the necessary velocity without punishing recoil.  Other bits of the requirement are within the capability of a 40mm MGL with improved ammunition

When I was really looking at it, the best alternative to the 40x51mm AB was the M72 LAW Airburst. 

MR800 FCU = 1.54lbs

M72E11 AB: 10.6lbs

x3= 31.8lbs

Total = 33.34lbs

Milkor 40mm w/ Multi Ray 800 = 16.14lbs

24x 40x51 MV = 15.84lbs

Total = 31.98lbs

You get less 'shots' - obviously - by going with the M72 AB. But each shot with the M72 is an order of magnitude more devastating. 4000 pre formed tungsten fragments, with a 15m lethal radius. And thats a 'real' lethal radius in that the tungsten pellets are penetrating 12" of ballistics gel, not the laxer standard test of penetrating a 2mm aluminum sheet used for most HE tests. 

For reference, the STK Airburst 40mm uses 330 tungsten pellets. 

This makes the system:

-More lethal

-More tolerant of aiming error 

-Capable of taking out multiple targets with a single blast 

Abandoning 40mm in favor of a 'M72 Squad' would also allow greater operational flexibility:

-M72 Airburst for infantry / counter defilade 

-M72 Anti Structure for urban warfare 

stancrist said:

HEDP was opted for in order to have one ammo type that could be used against both personnel and light armored vehicles. HE is ineffective against light armor, so grenadiers would have to carry reduced amounts of two ammo types:  HE and HEAT

I'm curious how much effect a little 40mm HEDP would have against a modern armored vehicle? 

I know they can burn through a pretty thick chunk of steel, but how much effect do they achieve once they've burned through? 

I love the idea, but M72s are something like $1,500-2,000 per shot. That will prevent adoption of your idea, until it becomes necessary.

Farmplinker said:

I love the idea, but M72s are something like $1,500-2,000 per shot. That will prevent adoption of your idea, until it becomes necessary

Well, the Army and Marines are both ordering upgraded M72's already:

https://www.marines.mil/News/News-Display/Article/2299100/marine-corps-releases-solicitation-for-rocket-system/

And they used a number of them in Iraq and Afghanistan; not to mention using $90k Hellfires for individual men and Javelins as anti building weapons etc. 

So I think the price is probably not too high, especially since they're only being fired in combat, and the overall lethality to price ratio is favorable. 

I think a bigger hurdle is institutional -convincing them to ditch grenade launchers for rocket launchers. And then re-jiggering the squad / tactics to make it work. 

Farmplinker said:

I love the idea, but M72s are something like $1,500-2,000 per shot. That will prevent adoption of your idea, until it becomes necessary.

Assuming they are only $2,000 then what would be the issue? 30 rounds of 40 mm grenade ammo won't be much cheaper.

I suspect the hope is the fire team will use 3 or 4 grenades for under a $1,000. It probably won't happen, but the Army will try.

Farmplinker said:

I suspect the hope is the fire team will use 3 or 4 grenades for under a $1,000. It probably won't happen, but the Army will try.

You guys keep trying to attach the concept of fiscal responsibility to the US army with zero evidence that they have ever tried. Their attempts to limit the cost of munitions appears to mostly be related to the exorbitant pricing by vendors and not to limit their usage. 

The UK sent some Milan posts to the Falklands with instructions to "only fire them at important targets". The squaddies then proceeded to fire them at every suspicious rock.

gatnerd said:

I'm curious how much effect a little 40mm HEDP would have against a modern armored vehicle?

I know they can burn through a pretty thick chunk of steel, but how much effect do they achieve once they've burned through?

Good questions.  Unfortunately, I've never come across  that info.