XM25 "good enough"

[Firn]

The UBGL is essentially an (almost) always ready-to-fire version of WW2-era rifle grenades that used muzzle cups (such as German Schissbecher).

Modern rifle grenades are descendants of those WW2-era rifle grenades that used a rather stokes-like principle (sitting on the muzzle).


The UBGL and stnad-alone GL designs add (just like the Schiessbecher) a certain fixed cost of mass. No matter how many grenades you carry, you gotta carry those 1-4 pounds of weapon.

Thus we have today the choice between
* rifle grenades with zero fixed costs (mass) thanks to ladder sights on the grenade itself
OR
* grenade launchers with fixed costs (mass), which in present GL designs is somewhat outweighed by less slow use (I wouldn't say 'quick' as long as you need to flip up sights or carry a carbine in ready position but have to switch to a stand-alone GL). The variable costs (mass per shot) is also smaller.

Recoil as a problem rather favours rifle-attached solutions, for the additional weight reduces felt recoil. A given warhead mass and a given trajectory (~muzzle velocity) will yield about the same recoil all else equal (weight and thus recoil differences between fin and spin stabilisation may occur, though).


In the end, today's rifle grenades have two niches:

(1) Whole small unit grenade salvo without many heavy GLs
(2) Large calibre grenades (see the Simon doorbreacher rifle grenade)

GLs have other advantages

(1) Potential exploitation of Medium-low pressure principle.
(2) Can be carried ready for fire in UBGL
(3) Can be a multi-shot weapon (revolver or pumpgun principle usually)
(4) already standardised
(5) No need for bullet trap or special ballistite blank cartridge
(6) Can be used on weapons of different calibres without aiming issues
(7) The limitation to few soldiers inherently leads to higher practice standard by specialisation in practice
(8) Propellant power is independent of rifle/carbine calibre and barrel length.

The French, Israelis and some other countries make still much use of rifle grenades.

I mostly agree with this summary.

It is interesting that early post-WWII AT rifle grenades shared the technology, warhead or even more parts with the missiles fired by rocket launchers. This goes for the French (AC58 - WASP 58), Swiss (Gewehrgranate 58 - Raketenrohr) and the USA (M31 HEAT - LAW72).

For direct fire the max. effective ranges seem to have been around 75 to 100 m. Used like spigot-mortar with rocket-boosted grenades ranges up to 550 m, although shorter ranges would have been the norm. Velocities of up to 75 m/s were achieved, but with 7,62 mm blanks and as said with a rocket boost. Not much compared to the claimed 250 m/s of the Wasp and still a lot slower than the 145 m/s of the LAW72.

The Swiss army used the training rifle grenade 58 to lay cable across obstacles, something which was already done in WWII.

All in all I could imagine those niche uses ( points taken partly by Fuchs) with modern assault rifles.

(1) Whole small unit grenade salvos (HEDP, etc)**
(2) Large calibre niche grenades (SIMON, smoke grenades)*
(3) Cable, Grapple, Cordex projector


All of them should be bullet-trap or -through types. If practical, the lighter rifle grenades (HE/HEDP) could also double as defensive handgrenades, like some German WWII ones.

*Heavy AT grenades don't seem to make sense enough compared to light rocket launchers like the LAW72 to develop, train and carry them.

**Light mortars have taken part of that role, even if the rifle grenades are of course a different kettle of fish.

P.S: I guess Schissbecher is a typo

[Fuchs]

Some typos happen unconsciously, but honestly...

It was a stupid design, about as much over-engineered as the 5 cm leGrW 36 (platoon mortar). German engineers of the 30's were totally in love with spin stabilisation and neglected fin stabilisation (see also Rz 65, Nebelwerfer 41).

This, by the way, enabled the 8th air force to use its quite poor heavy bomber designs (which were mere target practice for fin-stabilised low-tech R4/M rockets!) in the first place.

[Compost]

XM25 could be “good enough” for use in some kind of adventure park but virtually useless everywhere else. See post 928 on Roles and Weapons with the Squad.

In the end, today's rifle grenades have two niches:

(1) Whole small unit grenade salvo without many heavy GLs
(2) Large calibre grenades (see the Simon doorbreacher rifle grenade).

That first niche would require prompt supply of spare rifles, carbines and attachments to replace those damaged or wrecked delivering volley fire during operations, and earlier in range practice and field exercise ?

What useful niches (other than salvo line throwing) are left when a section/squad typically has hand grenades, UGLs and demo charges plus Armbrust, M-72 or suchlike; and when a modern platoon can have a 60mm handheld mortar (issued or attached) and also one or more 40mm MGLs ?

[Compost]

It has been pointed out that lack of calibre makes for confusion. Can sentence be corrected?

[Fuchs]

GLs have other advantages

(1) Potential exploitation of Medium-low pressure principle.
(...)

I am disappointed. Why did nobody point out that rifle grenades inherently kind of exploit the high-low pressure principle?

------------------------

@Compost: Why should a salvo of rifle grenades wreck the weapons? The rifle/carbine is largely unaffected by the use of rifle grenades.

UBGLs and MGLs will typically not be together in a small unit. 40 mm medium velocity ammunition also puts a bold question mark behind a platoon ("commando", "light" or "patrol") mortar since it has ~700 m range and enough physical effect to achieve similar psychological effect.

[Compost]

Compost: Why should a salvo of rifle grenades wreck the weapons? The rifle/carbine is largely unaffected by the use of rifle grenades..

First, “bullet-trap or –through designs” produce a pressure pulse that is higher than the normal pressure for which the rifle or carbine was primarily designed. For grenade launching to be approved that higher pressure must be within safety limits. Perhaps that also means there are no cumulative affects and my residual concern there is wrong.

Second, the user expects the recoil to be higher and anyway to achieve range a recommended method of firing is with the butt grounded. If/when the weapon is held down with inadequate pressure – especially against a hard surface – the butt is liable to damage together with any frangibles attached to the weapon. That is likely to occur due to haste and stress during operations and exercise and training. An expert is unlikely to make that mistake but in volley/salvo fire only some will be rifle grenade experts.

UBGLs and MGLs will typically not be together in a small unit. 40 mm medium velocity ammunition also puts a bold question mark behind a platoon ("commando", "light" or "patrol") mortar since it has ~700 m range and enough physical effect to achieve similar psychological effect.

Agree UGLs and MGLs and mortars will typically not all be together in a small sub-unit such as a section/squad but at least two of the three are on issue to some modern platoons. The USMC platoon now has one or more MGLs and its squads have UGLs able to fire LV and MV rounds.

However, a light mortar is longer ranged than 40mm MV weapons and can launch a significantly heavier and more damaging weight of ‘munitions’ particularly including HE, line, smoke and exotics such as para-cameras and micro-UAVs. If a light mortar is needed by a USMC platoon then a 60mm can be obtained from the company weapons platoon.

Hence my phrase: “when a modern platoon can have a 60mm handheld mortar (issued or attached) and also one or more 40mm MGLs “.

In line with that concept, the Br Army platoon has regained a light mortar and its sections have UGLs. I believe that 60mm mortar would be carefully kept on issue (although not invariably carried on light infantry operations) even if the platoon were to gain one or even two of the increasingly attractive 40mm MGLs.

[Fuchs]

This is the very first time that I hear about some "pressure pulse" problem associated with rifle grenades. I have some physics skills, but I can only imagine a tiny effect after the time when the bullet reaches the muzzle. The grenade might act as a cloture (hardly with bullet-thru, though) for a very, very short moment.

I doubt that this has any measurable effect, since barrels have a decent safety margin anyway.


About the buttplate damage; again entirely new to me. Soldiers do a lot with their rifles and rifles have to be tough anyway. The recoil of a rifle - even with a heavy projectile - should be well within the limits of normal harsh treatment.

[Ken White]

The only problems with rifle grenades is that they are heavy, inaccurate and tie up the rifle from which they're fired. Due to those shortfalls, they are disappearing from inventories and rightly so. A 40mm under a rifle is a far better solution.

Whether the XM-25 is going to be a plus for combat -- heavy combat -- remains to be seen. For combat operations like the current efforts, it does what it's supposed to do -- which is more than can say for most of the tripod or vehicle mounted AGLs. Those things are significantly overrated. Though they are fun to play with...

Last I heard, Canada proposed to replace their 60mm mortars with 40 AGLs. I hope, for their sake, that's not true...

[Kiwigrunt]

This is hearsay but I was led to believe that the NZ army tested rifle grenades prior to adopting the 203 and the recoil would rattle the AUG to bits. I have read suggestions regarding the British CLAW of the nineties knocking the SA80 scope out of zero. But the 203 is said to do that to the standard scope on the AUG as well, although I never experienced that.

The French, long-time users of rifle grenades, also seem to be moving towards UGLs.

[Compost]

This is hearsay but I was led to believe that the NZ army tested rifle grenades prior to adopting the 203 and the recoil would rattle the AUG to bits. I have read suggestions regarding the British CLAW of the nineties knocking the SA80 scope out of zero. But the 203 is said to do that to the standard scope on the AUG as well, although I never experienced that.

The following paras on rifle grenades summarize what I have been told/instructed and read over time combined with some assumptions. (Due to ignorance, the affects of gas being bled off into the cylinder during the grenade launch is largely ignored.)

Launch of a bullet-trap or bullet-through rifle grenade does include some energy simply transferred from the bullet to the grenade. However, the grenade is mainly projected by gas and that is the basic reason for the higher recoil force.

Depending on the configuration of the muzzle and/or projector, the rapidly expanding jet of gas driving the bullet out of the barrel may be initially directed upon the whole or only part of the driving surface of the grenade. Whole exposure (in a chamber with a cross-section larger than the bore) or partial exposure increasing to whole exposure as the grenade moves forward would seemingly be accompanied by a reduction in the gas pressure which was until that moment restricted to the bore. However that reduction can be almost instantaneously overtaken by an increase as the continued expansion of the gas jet is restrained by the slowly accelerating grenade.

Rifle ammunition is designed to burn propellant to initiate the movement of a bullet and spin it up to achieve a particular muzzle velocity. Irrespective of whether the propellant is fast- or slow-burning and whether that propellant is exposed and burnt at a uniform or an increasing or reducing rate, the bullet is started and accelerated by varying pressures of gas. Typically a gas pressure peak is generated early during passage of the bullet up the barrel and the bullet is stabilised although it can still be accelerating as it exits the muzzle due to an ( ‘extinguished’ or still-burning) gas jet that continues to operate but at a lower pressure than lower in the bore. To avoid violent operation of the bolt unlocking mechanism and of the bolt itself, a rifle and its ammunition are designed so that pressure in the barrel has been somewhat reduced before any gas reaches a tapping port into a recoil cylinder.

A particular feature of the rifle grenade is that it introduces another pressure peak and also adjacent high pressures that all occur close to the muzzle. Dependent upon grenade weight, that second pressure peak can be higher or much higher in a rifle than the ‘normal’ pressure peak produced when firing a single round of ball ammunition.

The time span during which the grenade-related pressures operate can be referred to as a pressure pulse. In a short-barrelled carbine that second peak will tend to reach a higher pressure and consequently duration of the pulse will be reduced.
All gas pressures generated in the barrel are also directed backward to the firing chamber and via the bolt to the bolt locking mechanism. If the intended use of a rifle or carbine includes the firing of rifle grenades, then the bolt locking mechanism must be more strongly engineered. That applies especially to the lugs of a forward locking bolt, and the receiver that houses a rear locking bolt

Additionally the second peak and adjacent pressures occur as gas is being tapped from the barrel to drive the bolt-unlocking cycle. To avoid violent unlocking it is preferable to suspend or reduce gas tapping. For example the gas regulator of a 7.62mm FAL/L1A1 SLR was routinely adjusted to close off the gas cylinder before firing a ballistite cartridge to launch an Energa AT grenade. Failure to close off often resulted in a bent piston rod.

My books on ballistics and small arms are currently packed in boxes, and this topic will be long gone before they are unpacked. So am interested to read any post that identifies an authoritative and readily accessible source, or provides detail that expands on or contradicts the above.

But in summary there is at least one good technical reason to avoid use of rifle grenades.

[Fuchs]

Keep in mind that you do not need to use heavier rifle grenades than barrel-launched grenades, and you don't need to use them at a higher velocity.

FN Bullet-thru: 320 g
40x46mm: 230-250 g

This means all higher recoil would quite by definition be an intentionally accepted by-product of higher performance.

[Compost]

Air-burst 40x53mm HV cartridge grenades and integrated FCS-fuzesetters are already available for several types of 40xmm AGLs.

A recent report claims the USMC is seeking air-burst capability for its 40mm UGLs and MGLs: see http://www.military.com/news/article...st-weapon.html

During the last few years Germany, Israel, Singapore and South Africa have each been rumoured to be developing FCS-fuzesetters or sights with dial-in fuzesetters for air-burst 40x51mm MV and also for 40x46mm LV cartridge grenades. So candidate systems for USMC evaluation could include several of these.

[Compost]

Last para of item 72 is misleading. Copy of the recent USMC RFI for airburst 40mm cartridge grenades is available at
https://www.neco.navy.mil//synopsis_...13_Oct_11.docx

RFI specified proximity fuzed 40mm LV grenades to engage defilade targets between 30 and 150 metres. Ammunition to be compatible with M203 and M32 launchers without requiring any modification or addition of equipment. RFI closed on 5 Dec 2011 at 4PM.

[jcustis]

I submitted an idea to the Marine Enhancement Program a few years ago, recommending the exploration of an indirect fire sight to allow for the M203 to be employed in an IDF mode, similar to the the sling technique that has been all but forgotten.

The MEP folks said it would be pushed past Gunner Eby at that time to review, and it seems it didn't stick.

[Compost]

The British have raised a supply contract for 40mm MV/ER cartridge grenades to be employed in a feasibility study with in-service single-shot weapons. The contract specified six grenade variants – HEDP and five types of smoke, marker and illuminating. That variety is generally similar to the types of bomb previously fired from their 51mm platoon mortar.

See: http://ted.europa.eu/udl?uri=TED:NOT...3:TEXT:EN:HTML

If testing is successful then possibly the Canadians will follow and be followed in alphabetic order by Oz and NZ.

[davidbfpo]

There is an old thread Canadian 60mm problem, which maybe relevant:http://council.smallwarsjournal.com/...ead.php?t=5692

[Compost]

That 60mm mortar problem was well considered by Canadian CAPTs Rintjema, Boucher and Erkelens as reported in “ Infantry Company Crew Served Weapons “. Their report is available at

http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

The British Army seems to generally share/agree with its main conclusions: summarised as infantry company fire based on 60mm mortar and 84mm CG RclR with 40mm HV AGL introduced in preference to 12.7mm HMG.

Hence believe British are now considering the 40mm MV grenade capability as a complement to their recently gained 60mm platoon mortar. The 40mm MV seems particularly suitable for section use and close-in tasks where even the small bombs of the 51mm mortar were previously useful.

[Fuchs]

Can anybody explain to me why the excessively heavy M3 Carl Gustav (still not exactly lightweight in its most recent version) is so very popular among anglophones?

Nothing, absolutely nothing in its published specs points at a superiority over the likes of the already phased out LRAC F1 STRIM* and similar weapons.
Is it all about the (recently developed) fancy munitions?

For example, the U.S.Army finally introduced the M3 CG for general infantry and promotes this fact as if they had invented something great, but the marines already had their equivalent already for three decades (an Israeli 70's design).

Sometimes it seems as if the people's capacity to think about weapons and munitions cannot reach beyond a few marketing stars, ignoring more than 90% of what's actually available.


* An export success story in the francophone world.

[TAH]

Saw the story the other day. IIFC, the major point was that it had greater range over the disposable AT-4s currently being carried.

Ammo for it is also "in the system" as our rangers got it back in the 90s.

I had recommended it as a replacement for the old 90mm recoiless rifle when I worked at the Engineeer Center. My thoughts were it was more flexible then the 90mm because it also had the capability to fire both smoke and illum rounds. Nice options for a combat engineer as part of a breaching effort, smoke to screen and illum for thermal marking.

They went with the Javilin ATGM instead. Go figure.

TAH

[Fuchs]

Saw the story the other day. IIFC, the major point was that it had greater range over the disposable AT-4s currently being carried.

That's a function of barrel length and munitions, which are about identical.
The effective range is coined by the aiming device, and as Germany shows with its Panzerfaust 3IT-600, you can also attach an electronic fire control system to a disposable ammunition tube. In fact, the U.S.Army could have adopted the Dynarange sight 15+ years ago and simply attached it (with slightly adapted dimensions and computing variables) to its AT4s.

The trade off between reloadable and disposable is rather the fixed weight (launcher) and weight per shot (less for reloadable).