schnuersi said:

I agree that a ~250 g grenade and ~100 m/s seem about right. But I am not convinced that it has to be 40 mm in diameter. There are 23 mm shells ~200 g. So it should be doable to get a usefull 250 g grenade of 25 mm diameter or less. This would offer conciderable advantages for feeding. Not only for magazine or drum options for the squad support weapons MV ammo but also for the HV AGL ammo. The latter would also benefit from the improved aerodynamics

I'm curious how much aerodynamics / shell shape plays for the range of these subsonic munitions? Even the 'High Velocity' 40x53mm has velocity comparable to a .38 Special snub nose revolver or mid grade air rifle....Especially as the grenade probably needs a rounded, blunt nose to maximize the amount of fragmentation pellets that can be packed into the nose for forward firing airburst.

...

I say 40x51mm is what OICW should have been mostly in terms of what I see as the logical, incremental development chain that should have been used for developing counter defilade / airburst grenade launchers:

1. Develop FCU for MK19 AGL (large Gen 1 FCU size less a hinderance for AGL)

2. Develop Airburst 40x53mm ammunition (larger shell offers more room for Gen 1 fuse)

3. Work on refining both: improved frag shells, smaller fuse, reduced FCU size / improved performance 

4. Field rifle mountable FCU as technology when tech improves enough to allow miniaturization. Begin use with existing 40x46mm M203 and ammo.

5. Develop something like 40x51mm airburst, using airburst projectile developed in steps 2-3, but at a tolerable recoil level for shoulder use

6. Field either improved 40x51mm underbarel launcher and/or dedicated 40x51mm multi shot launcher paired with FCU from step 4

Instead they jumped straight from M203 to semi auto 20mm airbust high velocity rifle paired with 5.56 integral micro assault rifle...with predictable poor results. 

gatnerd said:

I say 40x51mm is what OICW should have been mostly in terms of what I see as the logical, incremental development chain that should have been used for developing counter defilade / airburst grenade launchers:

You see, your plan sounds like a logical evolutionary development, which is exactly opposite to persistent American love to "revolutionary", "game-changing" and "quantum leap" approach to almost every military development

gatnerd said:

Instead they jumped straight from M203 to semi auto 20mm airbust high velocity rifle paired with 5.56 integral micro assault rifle...with predictable poor results.

Actually, there was some development effort on an intermediate weapon between the M203 and the OICW. 

The EX 41 grenade launcher seems pretty close to your Step 6, but apparently the ammo was too powerful.

mpopenker said:

You see, your plan sounds like a logical evolutionary development, which is exactly opposite to persistent American love to "revolutionary", "game-changing" and "quantum leap" approach to almost every military development

We do love that sort of stuff, and to be fair it has worked out pretty well from time to time.

That said, other then SPIW, I'm hard pressed to think of another US weapons program - for basically any type of weapon - that jumped as many stages of incremental development as the jump from M203 to OICW. That was like going from the Beeper to the Iphone in a single bound. 

stancrist said:

The EX 41 grenade launcher

That is an interesting one, and certainly way more incremental then the M203-OICW jump. 

Seems like the downfall there was going with a 240g at 152m/s - recoil was described as being 'punched in the face.' 

gatnerd said:

I'm hard pressed to think of another US weapons program...that jumped as many stages of incremental development as the jump from M203 to OICW. That was like going from the Beeper to the Iphone in a single bound.

Would incremental development really have made a difference?  It seems to me that the issues with OICW were not a result of the simultaneous development of a fire control and airburst munitions, but due to excessive weapon weight and a warhead that was too small.

gatnerd said:

I'm curious how much aerodynamics / shell shape plays for the range of these subsonic munitions?

In contrast to what one might think aerodynamics are very important for subsonic munitions. To some degree even more important that for super sonic ammo.
So there is potential for quite some improvement.

gatnerd said:

Especially as the grenade probably needs a rounded

Which would be good for subsonic aerodynamics.

 

gatnerd said:

That said, other then SPIW, I'm hard pressed to think of another US weapons program - for basically any type of weapon - that jumped as many stages of incremental development as the jump from M203 to OICW. That was like going from the Beeper to the Iphone in a single bound.

I can think of several out of my head. Not only US but German as well...
and usually they all failed. But after the program being shut down usually the technology that worked is transphered and used for anther program. So allmost nothing ever fails entirely.
It should also been kept in mind that some programs are stopped. Even though they have shown potential or have even actually worked. The funding is moved somewhere else. Lobbying and politics also play a major role in this.

gatnerd said:

Seems like the downfall there was going with a 240g at 152m/s - recoil was described as being 'punched in the face.'

Which seems to be caused by unrealistic range expectations. The M203 has an effective range ~300 m and the EX 41 was designed with 1500 m range. A five times increase. Which puts it firmly out of the typical engagement range of a squad and into support weapons territory. In other words it wasn't really a replacement for the M203. It was a non crew served Mk19.

I think its a problem of bad project management. There obviously seems to be a capability and power creep issue. The XM25 and OICW also suffered from this. If they had kept the required range down in a realistical and usefull level (500-600 m) instead of pushing it out to 1000 m, again well behond the engagement envelope of an individual infantry man or squad, chances are they would have produced an actually usefull weapon.

A decent intermediate step would have been giving up fantasies of taking out BRDM and BMP with your blooper and replaced the LV HEDP with  40mm MV firing bounding HE, ideally with the heavier 40x53 projectile, followed eventually by a product improved version incorporating PFF with computer aided fragmentation optimization, fuze miniaturization, and mid fuze design.

The first could have been done in the 80s-90s, the second in the 2000s, and both would have been superior to what we're still running in both lethality and range. By 2010 programmable airburst would be doable, but I don't even think the price per round justifies it, bounding HE is the 80% solution.

It's 2020 now, complement the above with something like pike and the combo can pretty much fill the OICW / defilade killing role at squad, with the pike also addressing the problem of harassing fire from "yonder PKM" shooting from silly distances.  Add on weaponized drones that fit in a 40mm grenade pouch, the tech is there to do it today, it requires no launcher so no launcher weight, and each round is put right where you want it out to multiple km. Even if the latter were neutralized in a heavy EW environment, you can still fall back to the other stuff that hasn't gone anywhere.

The anti defilade capability is mirrored at platoon with CG / 60mm MAPAM, both airbursting, and maybe something like the Chinese 40x53 critter with thermals, LRF and ballistic computer. In the grand scheme of things the costs are trivial compared to a single F-22, and it's right there on the table. Like optics on rifles we're going to look back and wonder why we didn't do it sooner.