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Subject: 25mm vs 40mm grenade launcher controversy
Jeff_F_F    7/6/2007 4:54:31 PM
So what are your views on the advantages and disadvantages of the proposed 25mm OICW/OCSW grenade system vs current low velocity and high velocity 40mm grenades?
 
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Jeff_F_F    from 6.5 vs 6.8 thread...   7/6/2007 4:55:18 PM

Yimmy       7/5/2007 2:01:37 PM
Why the fad for 25mm grenades?

They lack the HE capacity of 40mm grenades in the UBGL role, while in the direct fire support role they lack the large beating zone of a 7.62mm GPMG, while they lack the long range flat trajectory of the .50 cal HMG.


 
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doggtag       7/5/2007 6:21:16 PM

Why the fad for 25mm grenades?

They lack the HE capacity of 40mm grenades in the UBGL role, while in the direct fire support role they lack the large beating zone of a 7.62mm GPMG, while they lack the long range flat trajectory of the .50 cal HMG.




Why the fad?
Because that's what the US Army dictated the OCSW Objective Crew Served Weapon was going to be.
Sure beats me why they didn't opt for improving on the 40mm versions.
My guess is they wanted something with a higher muzzle velocity that didn't rely on lobbing its shells to maximum ranges, wasn't as susceptible to high cross winds,
something that could incorporate a built-in fire control computer that could lase distances to targets and program a round to detonate near enough where intended yet not be so heavy and cumbersome between the gun and its ammo that it took 3+ men to carry it all around.
 
So in the end, this is what we (US Army) look to be getting, the XM307/XM312 convertible machine gun, adaptable to fire the 25mm grenades or 12.7mm bullets.
 
link it's a cheesy YouTube video, taken from that show Future Weapons)
 
 
 
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flamingknives       7/6/2007 5:53:43 PM
It was my impression that the benefit of the 25mm round was that it could hit targets behind a defilade, which is hard or impossible to do with any other kind of direct fire weapon.
 
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Yimmy       7/6/2007 6:03:23 PM
I don't really hold an opinion either way.  The 25mm grenade launcher is just another new toy, and a nice sounding toy at that.  I am not quite sure where in the infantry (or other) battalion it would find a place however.  I am not sure calling it a grenade launcher is even appropriate, as to me it sounds more of a low pressure cannon, though I can't claim to know how long the cases are.  Certainly, it sounds somewhere between the .50 cal HMG and the 40mm AGL's.

It is not a replacement for the .30 cal GPMG.  This weapon has been a standard since before WWII, and it will stay such into the far future (just look at the failed attempt by the British army to replace it with the .22 cal LSW).  The GPMG in the sustained fire role provides direct firepower out to 1800m's, while it produces a large beating area to suppress the enemy, and its ammunition is reasonably light.  In contrast the new 25mm weapon, even if the gun itself is super light weight, will still have issues with bulky and heavy ammunition, and as a result a much reduced sustained rate of fire.

The new weapon lacks the overall brute firepower of the 40mm AGL, while it lacks the long flat reach and AAA abilities of the .50 cal HMG.  In todays conflicts it could be just the right compromise of the two for light forces.  I can't see it being popular on armoured vehicles though, where the vehicle can withstand the recoil of a real 20/25mm cannon.


 
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Professor Fickle    I saw this thread coming!   7/6/2007 10:22:08 PM

>    >“…Or do half a dozen 25mm High Explosive Armor Piercing rounds, better placed due to their flatter trajectories, give a better anti-armor (or anti materiel) perfomance than half a dozen 40mm HEDP grenades?...”

 That, HELL Yes !

BOTH are quoted on having 50 mm penetration.

 From  Gary's U.S. Infantry Weapons Reference Guide
  The high explosive dual purpose round can penetrate 2 inches (50 mm) of armorplate, 12 inches (300 mm) of pine logs, 16 inches (400 mm) of concrete blocks, or 20 inches (500 mm) of sandbags at ranges up to 1,312 feet (400 m). 

I saw this thread coming!

>>

“…One could start another CALIBER discussion on 40x53mm vs. 25x59mm (mk-47 vs. xm-3017)…more ammo or more powerful ammo, more accurate or more devastating, cheaper ammo, COMMON AMMO, the next ammo 25mm… etc…”




 
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Sabre       7/9/2007 12:50:24 PM

The new weapon lacks the overall brute firepower of the 40mm AGL, while it lacks the long flat reach and AAA abilities of the .50 cal HMG.  In todays conflicts it could be just the right compromise of the two for light forces.  I can't see it being popular on armoured vehicles though, where the vehicle can withstand the recoil of a real 20/25mm cannon.
I have often wondered why 20 and 25mm cannons aren't more widespread.  You don't even need a turret, they have been ring-mounted on a few vehicles.  The French used to have a 20mm co-ax on their tanks, and way, way back in the day when the Humvee first arrived, it was going to have a 25mm cannon on a ring-mount, in the Light Cavalry units (I even have an old -19 series field manual showing the Light Cavalry Troop with a mix of 25mm and TOW Humvees).  You can have a "cocktail" munitions once you get to 20mm and above... I always thought that it was obscene to have a new, multi-million dollar M1 with an ancient, worn-out .50 cal on it.  The M2 .50 cal's my unit had were junk - and we had some really sharp armorers constantly repairing them.  Does the M312 have a higher rate of fire than the 260 rpm of the M307?
If the new 25mm grenade means that tanks finally get a weapon with a teeny-weeny bit of indirect fire capability (and an option besides their very limited supply of HE 120mm), then great.  You don't always have a Bradley (or other AICV) around to hose things down (and they can't own deadspace).  It may take a 40mm grenade 22 seconds to reach out to 2000m, but that is still a little faster than the 60mm mortar that Merkavas have.  I don't have much against 12.7mm, but it is amazing how much ground you can tear up when you hold down the trigger on a Mk-19.

 
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VelocityVector    Sabre   7/9/2007 2:58:15 PM

Anti-aircraft capabilities of low-velocity 40 and 60 mm grenade launchers?  Expense of cannon with roof mount?  Effect at very short range either type?  12.7 mm is versatile and relatively cost-effective in comparison.  Ideally you might have a tank platoon mix but combined arms already addresses that in theory.  I have no background in armor and won't be offended by sharp criticism on the subject, so let fly ;>)

v^2
 
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flamingknives       7/9/2007 5:02:22 PM
12.7mm MG would have exacly no effect on a modern aircraft. It might scare off an attack or recon helicopter who strayed too close, but typically the Helo will see you first and attack from well out of range of a HMG.

If you want AA on a tank, VSHORAD missiles or AA capability of the main armament are the way to go as they have much better range and are much more lethal, so it would make sense to fit a flex mount more suited to engaging ground targets with less impact than a main gun round.
 
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Yimmy       7/9/2007 5:16:23 PM

12.7mm MG would have exacly no effect on a modern aircraft.

Why not?  Tracer climbing through the air is bound to un-nerve any pilot.  And while helicopters are prolific, helicopters which can destroy armoured vehicles from several km's away are not.  The vast majority of helicopters fulfill utility roles, and are not armoured close to the extent necessary to resist .50 cal fire.

 
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flamingknives       7/9/2007 6:01:07 PM
Well, a modern fast jet is going to be several thousand metres out of your vertical range, nevermind lateral offset.

Anyone flying a utility chopper over an enemy tank column deserves to get shot to pieces. Plus utility choppers are rarely a threat to armour. If you can kill a tank you can usually do it from several time MG range. Splash it with airpower and let tanks do tanking.

Tracer does unnerve pilots, but it only works if the hostile pilots are making gun-runs.

I can see a point to an AAMG on a tank - to make things a bit difficult for the enemy and stop him taking liberties like dropping napalm cannisters from utility choppers. But in any war where the enemy has a functioning airforce he'll be using the standoff stuff against your front lines. 
 
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Horsesoldier       7/10/2007 4:39:25 PM
Sure beats me why they didn't opt for improving on the 40mm versions.
My guess is they wanted something with a higher muzzle velocity that didn't rely on lobbing its shells to maximum ranges, wasn't as susceptible to high cross winds,
something that could incorporate a built-in fire control computer that could lase distances to targets and program a round to detonate near enough where intended yet not be so heavy and cumbersome between the gun and its ammo that it took 3+ men to carry it all around.
 
The initial idea was to replace the big, blocky 40mm grenade (which has about a 1:1 length/width ratio) with something more ballistically efficient.  The goal they wanted with the OICW (may still want it, for whatever it is worth) was a grenade launcher capable of engaging out to 1000 meters with the weapon's onboard optics and ballistic computer coupled with airbursting ammunition.  The idea was to transform infantry combat from a sub-300 meter event to a 1000 meter and below endeavor.
 
The 1000 meter range requirement is largely why the OICW could never make weight.due to the optics required as well as the recoil compensation system and such associated with a 20mm (later 25mm) semi-automatic, magazine fed grenade launcher.  Other R&D, including both the Austalian and Swedish efforts, have pursued the airburst ammo idea but have not tried to get that 1000 meter range, making them lighter.  I'd venture to guess that the 1000 meter engagement range is an irrelevance, at least in the current low intensity kind of conflict, since even with optics it's extremely hard to detect, positively ID as hostile, and effectively engage targets at longer ranges.  If a x4 or so power scope can't get you a good shoot/no-shoot decision and engagement on a guy with current weapons, I'm not sure the optics on the OICW will translate into a lot of 1000 meter engagements against insurgents if you handed them out tomorrow.  (Now, a conventional infantry platoon advancing on your position, etc., would be another story I suspect -- but also suspect that R&D money is going towards LIC applications for small arms at the moment.) 
 
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