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.

stancrist said:

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

I think incremental improvement absolutely would have prevented OICW/XM29. Namely as starting with 40mm as the first increment would have likely prevented the pursuit of 20-25mm, or at least delayed it to a point where its failure wouldnt have mattered as an existing 40mm AB already would have existed. 

Likewise, incremental experience with early giant FCU's paired with a M16/M4+M203 would have likely disabused any fantasy of a semi auto grenade launcher+assault rifle+fcu combo, as the basic M4/M230/FCU already would have been quite heavy. 

Incrementally, if the FCU and AB were really nice, it also could have negated the pursuit of a multi shot grenade launcher, as the FCU+AB shell may have been found effective enough to not warrant a dedicated large launcher. 

...

Kind of further supporting this, after OICW/XM29 failed, we saw private industry basically replicate steps 1-6 on their own via incremental improvement. First a FCU for the MK47, then STK and Rheinmetall developing AB 40x53 and their own FCU's, then development of 40x51MV and 40X46ER with pre-fragmented casings, and now here we are with SSW as the dedicated multi shot 40x51mm ab launcher.

schnuersi said:

In contrast to what one might think aerodynamics are very important for subsonic munitions

How would the shape of 40mm be improved for subsonic aerodynamics?

gatnerd said:

How would the shape of 40mm be improved for subsonic aerodynamics?

The shape itself allready is pretty good. The boat tail of the base could be more pronounced.
A smaller diameter but longer shell of the same mass would have less frontal area and thus less drag.
A fully optimised projectile almost looks like a boat tail bullet with a long ogive and a fully rounded boat tail but moving backwards. The boat tail is actually the boat front. This of course would be an extreme but with a long small diameter projectile its far easier to get close to the optimum with a usefull and easy to produce ammo than with a short and stubby one like the typical 40 mm grenades.