gatnerd said:

I have always like FN's 'OICW Lite' implementation with the original F2000

I rather liked it when I first saw it many years ago.  But I now think it's much too heavy (see my comment about rifle weight in my reply to Emeric).

More importantly, the "OICW Lite" is also too limited by the 40mm grenades.  It seems to me that bursting munitions need to be of larger caliber.

Think something much closer in size to this:

stancrist said:

Heh, heh.  Cute, but no.  Too inefficient.  The soldier has to lug around a heavy rifle and its ammo, which reduces the number of HE rounds carried.

So, what would be an "efficient" way to launch a ~1 pound HE warhead?

Maybe a lighter rifle, with lighter ammo?

stancrist said:

And is your proposed solution even a viable option with the XM5?  Seems like that big round thing on the muzzle would be somewhat problematical.

That big round thing is a QD variety, isn't it?

So, just use a QD suppressors that could be mounted on a standard 22 mm OD flash hider.

EmericD said:

So, what would be an "efficient" way to launch a ~1 pound HE warhead? Maybe a lighter rifle, with lighter ammo?

I'm thinking maybe a dedicated grenade launcher, with a separate PDW for CQB.

EmericD said:

That big round thing is a QD variety, isn't it? So, just use a QD suppressors that could be mounted on a standard 22 mm OD flash hider.

Is it feasible to launch rifle grenades with an SBR?

How well does the HK416FC shoot rifle grenades?

stancrist said:

Is it feasible to launch rifle grenades with an SBR?

You need to leave 10 cm between the gas block and the tip of the flash hider, which is OK for barrel length above ~12.5" (I think that's SBR territory).

stancrist said:

How well does the HK416FC shoot rifle grenades?

Launching rifle grenades was expressively NOT a requirement for the F-C version (we bought it as a PDW, not a carbine or a rifle).

We could have required the F-C to be able to launch rifle grenades (and mount also a bayonet for good figure), and finish the competition buying an "infantry rifle" (capable of launching rifle grenades and using a bayonet) with a 14.5" barrel, and a "PDW" (with the same capabilities) with a 12.5" barrel.

That would have been pretty stupid.

Two questions about the use of rifle grenades:

1. During World War 1 the British Army ended up using old SMLEs as dedicated grenade launchers, with their stocks reinforced by wire wrapping, due to the hammering that the rifle got when used as a grenade launcher. Do you have to monitor and possibly limit the number of rifle grenades fired from individual rifles?

2. You discussed the time to achieve a firing solution for OICW earlier. However, is it recommended that rifle grenades are used in conjunction with some sort of rangefinder/known range where possible, to improve accuracy especially at longer ranges?

It strikes me that a bullpup-rifle is a much sturdier platform to fire a rifle-grenade from, due to the shorter length which results in increased overall stiffness of the rifle, in addition to the fact that bullpups usually have a much larger cross-section from the chamber to the stock, thereby resisting bending-moment much better.

Would it be more useful to have grenade launching platforms (say an AGL or a 60mm mortar) loaded onto some sort of unmanned ground and/or aerial vehicle?   Man portable heavy weapons -  even grenade launchers - always face compromises because of weight (limiting how much ammo can be carried compared to rifles)  GL also tend to be heavy (Especially multi-shot) and you need that because the recoil can also be high (especially if you want a high velocity to get more range)  and that forces more trade-offs between projectile weight and velocity and the recoil for a man portable weapon.  recoilless weapons don't have the recoil issue but still face tradeoffs in weight vs performance AND the need for countermass imposes its own constraints.   Thus, providing that capability in a separate supporting platform seems more worthwhile, and unmanned vehicles can come in a wide variety of forms. 

I'd expect the need for suppressive fire also remain so having at least some troops equipped with rifles that can be effective at longer and shorter ranges (including Designated Marksmen) would be desirable.    In that context I could see giving troops some kind of rifle grenade in small numbers to supplement a unmanned support weapons platform.

Failing that, something like Big Dog or some other robot to serve as ammo carrier might alleviate the weight requirements and work equally well for tube launched grenades, rifle grenades and small mortars and recoilless weapons.   At most the soldier has to carry the weapon and a smaller quantity of ammo.   I imagine the robot could also carry heavier support weapons like a Gustaf. 

PRM2 said:

1. During World War 1 the British Army ended up using old SMLEs as dedicated grenade launchers, with their stocks reinforced by wire wrapping, due to the hammering that the rifle got when used as a grenade launcher. Do you have to monitor and possibly limit the number of rifle grenades fired from individual rifles?

The first dedicated rifle grenades were heavy, for example the n°68 AT grenade weight was nearly 900 g, the Energa / super Energa / M31 were between ~650 and ~750 g, the recoil was significant and most of the time the rifle was fired with the stock on the ground, like a mortar.

The AP/AV 40 grenade we are using with the HK416 F weight around 435 g, and is designed to be shot from the shoulder, not with the rifle stock against the ground, or a wall, or a tree...

The force acting against the stock is less important when the rifle is fired from the shoulder, and we checked that the 416 could fire a minimum of 200 rifle grenades without damage.

PRM2 said:

2. You discussed the time to achieve a firing solution for OICW earlier. However, is it recommended that rifle grenades are used in conjunction with some sort of rangefinder/known range where possible, to improve accuracy especially at longer ranges?

This problem is driven by the effective range you want for your HE round.

There is a maximum amount of tolerable impulse, so if you want to increase the effective range, you need to increase the muzzle velocity and reduce the warhead weight accordingly. A smaller warhead will have a smaller effect, so you will need more accuracy, and ultimately a FCS of some sort.

AFAIK, I think that the ranging part of the shot should be devoted to the guy who is giving the orders and is maintaining the fire discipline, not to the shooter, and a ~400 g grenade with a range of ~350 m is still effective with even a rough aiming system.

Trying to shoot HE at a longer range than 400 m needs a significant increase of the launcher weight / sighting system / or a significant reduction of the grenade payload.

EmericD said:

Trying to shoot HE at a longer range than 400 m needs a significant increase of the launcher weight / sighting system / or a significant reduction of the grenade payload.

hm... there are methods to achieve the desired range increase without a significantly heavier grenade or more recoil impulse.

RAP! A rocket booster that fires after the grenade has been launched. It wouldn't have to be huge if the desired range increase is moderate. Like +150 m for 500 m range. Back in the day I read about projects for RAP rifle grenades but these have been about increasing the range for AT use of HEAT grenades. It should work for HE lobbing as well.

schnuersi said:

RAP! A rocket booster that fires after the grenade has been launched. It wouldn't have to be huge if the desired range increase is moderate. Like +150 m for 500 m range. Back in the day I read about projects for RAP rifle grenades but these have been about increasing the range for AT use of HEAT grenades. It should work for HE lobbing as well.

The 140 mm RAW was exactly that:

https://en.wikipedia.org/wiki/Rifleman%27s_Assault_Weapon