EmericD said:

so don't expect those 0.5 g of powder to produce any significant recoil-reducing effect

I'm not. The primary recoil-reducing effect would come from reducing the MV by shortening the barrel (this is in the context of something like a RAG-30 firing 30 x 29B ammo).

That then leaves the gas exiting the muzzle to be disposed of. On further reflection, I think that a suppressor might be more appropriate than a brake - or some kind of combination of the two, as the US seems to be playing with, for their new small arms.

EmericD said:

Yes, that's the irony.

And it's true, too.

LOL.  If you want irony, try this revision of what you wrote:

Despite the fact that the only multi-shot grenade launcher adopted by a western army during the last two decades uses a revolver action -- or perhaps because of it -- pretty much every multi-shot grenade launcher developed during the last two decades uses detachable magazines.

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.

Concur.

schnuersi said:

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.

250g is almost twice the weight of the 25x59mm grenade. 

Seems like it would make for a very long 25mm grenade?

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.