A Bradley mortar system?

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YelliChink 12/28/2006 1:46:51 AM

Supersonic aerodynamics is very different from subsonic ones. Compressibility of air is something very intrigue in the arena of knowledge. For subsonic projectiles, the cross section determines mostly how much drag there will be. For a mortar round, the tailfins are sharp edges, and sharp edges means turbulence, which implies unpredictability, in subsonic aerodynamics.

Now, back on French MCB-81 again. The crew have to learn three different kinds of gunnery: mortar, howitzer and tank cannon. Great, we have something like a Sherman tank with long range 81mm mortar capability. Tank guns usually have very large chamber compared to mortars. To make a gun that can accomodate 3 different types of ammo, which requires 3 different types of chamber size, propellant and any other factors that I still don't know, the breech design must be very interesting. Maybe that's why nobody actually purchased these multitaskers ever.

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doggtag 12/29/2006 3:37:09 PM

So much to reply to/pick apart, so little time!

Re: the concept of an M8-ish turret on a Bradley hull.

From having taken Bradley turrets out (requires a crane, after all),

the empty turret ring space within an M2/M3 hull (and providing we remove the infantry requirement to increase ammo stowage, as well as removing the TOW racks on the right side and 25mm ammo boxes on the left side internally of the hull), a similar-sized turret as fitted to the old M8 Howitzer Motor Carriage would fit quite comfortably (having seen the inside of an M8 years ago, even before I stepped foot in a Bradley, the 75mm howie and its cradle could adapt quite nicely into a BFV-friendly turret).

In fact, would it really be all that different, in the end, than the CVR(T) Scorpion's L23 turret, or that Saladin (L18?) turret that Australia fitted onto M113s?

Question being: is 3"/76mm ammo adequate enough for most expected targets?

Answer being: anything we shoot with 25mm & 30mm Chain Guns, 40mm AGLs, and 60mm mortars (as well as helos using 70mm rockets) could be engaged with 76mm gun-fired ammo from our theoretical "lightweight FSV turret".

But the problem we'd face is too many would start questioning as to why we'd use said caliber in a short tube and not adopt a longer tube capable of very effective APFSDS firing (76mm M32, 90mm CMI Mk8, etc...)

Does anyone know the performance characteristics of the HESH (High Explosive Squash Head) ammo the Brits used in the Scorpion?

Seems to me that those would be ideal for punching holes in walls that the US has been trying to "saw" out with 25mm & 40mm.

Besides, a hull full of 3-in ammo might offer a lot more target engagement options.

So yes, it does look like we might be formulating a modern-day "Shreman-esque" vehicle.

As for different charges for gun mortars: why can't we continue to utilize the typical clip-on type modular charge increments most mortars today use anyway?

As Jake and I mentioned booku times (here & other threads), the current gun mortars (notably, French MCB81) use the same series of charges to fire different ammo, be it HE types for support or AP types vs armor.

For the matter, how's it any different than any other tank gun, or artillery, firing different ammo types, each requiring various less- or more- powerful propellant charges?

As for nobody having bought any of the gun mortars:

one of my earlier posts on this thread mentioned Slovenia is doing just that (doesn't specifically say how many of the 8x8's will mount NEMO, but says NEMO is part of the purchase deal).

I don't know of any buyers for the MCB81,

but numerous examples of the various French-designed 60mm gun mortars have been in service since their inception,

mostly mounted in either the AML60 4x4 (or locally-produced copies), or as in the South African Ratel 60.

French industry itself produced two primary mounts, the Serval and the Mangouste (becoming increasing difficult to find worthwhile working links for these, but several books offer useful info).

Almost all of the gun mortar 60mm types ended up either in Central & South America, or mostly, African nations still wrapped up in local guerilla wars, and almost always mounted in some turret with coaxial MGs or alongside 20mm cannon.

But the problem all this (gun mortar debate) leads to is.

you get people who, since it's a lighter caliber weapon, aren't content with just using it as a fire support weapon, but they want to turn it into a high-velocity-capable tank killer also...just as happened in the case of the Stryker MGS (upon which I personally still feel those leftover ideals from the 1980s about 8x8 C-130-capable 105mm-armed tank destroyers finally came to fruition, regardless of how "battlefield-internetty" it is).

So they'd argue, "if we're thinking 60mm gun mortar, why not use 60mm hypervelocity guns?

blah blah blah...

If we really want a Sherman-ish thing that can keep company with infantry and provide lengthy fire support (more than 19 rounds available), then, yes, an 81mm gun mortar would be good: a new generation of shells could provide more punch than any 76mm rounds, and, in a direct fire role, we could even use a HESH/HEP type round against fortifications and walls.

...or what about a modern 25-pdr field gun in a turret?

(just a better installation than that woeful Bishop SP gun.)

Plus, after removing a Bradley's TOW & 25mm stowage, we could actuall

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YelliChink 12/29/2006 7:06:28 PM

High velocity cannons need propellant that burns very fast and creates very high chamber pressure (~40,000 to 50,000 psi). Mortars usually use propellant that creates several thousand psi. Thus, the immediate problem for MCB-81 type weapons is how to cope with the problem of different chamber design. One way is to design a filler to contain mortar shell into the bigger chamber. That is clumsy. The other way, which I believe is what French did in MCB-81, is to design special shell and high pressure cartridge for APFSDS rounds. The problem is that the approach to contain 40,000psi requires copper cartridge shells while that is not needed for, say, 4000 psi system.

http://www.inetres.com/gp/mili...

Loader assist is not the same as autoloader. 155mm and 160mm things are better with a loader assist. German's PzH 2000 actually can be hand loaded if load assist fails.

I believe what dogtagg wants is a company level thing that can deliver a 1-3kg projectile, which contain 300g to 1kg of Composite B or RDX to at least 1000m. The primary goal is to defeat enemy hard point or as counter-sniper weapon. Although US army use 81mm M252 in company level, other armies put 81mm mortars in battalion control. There are two solution to this one:

1. Put this capability to company support team.

2. Put this capability into platoon.

Since Mech Inf. Plt don't have platoon support team like their foot infantry counterpart, the second solution requires exactly what Russians had made into BMP-3. US Army TRADOC think of the first solution by putting 3 Stryker MGSes and 2 Stryker 120mm mortar carrers under company level. The only problem is, there is still no MGS in any SBCT yet. By the way, what does the unit sign of "a sausage with three meatballs" mean? I have never seen that one before.

SBCT is also interesting in battalion level because they actually put 155mm under battalion command.

I don't think that there is no consensus about the superiority of turrent-mount, breech-loading, enclosed mortar carrier over traditional mortar carrier. It only comes the problem when a design, like Stryker, has weight restrain. Given the organization of the US Army mech inf battalion, I would say that gun-mortar has no place in it. It is actually more practical to modify M24 Chafee's turrent system onto Bradley for that purpose. Bradley is made to battle with Soviet armor units, while BMP-3 is made to satisfy mech inf's dream. If you REALLY want a very big bomb at platoon level, than a spigot mortar fix mounted between the hatch of co and gunner may serve that well.http://en.wikipedia.org/wiki/B...

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doggtag 12/29/2006 10:51:24 PM

Nice post.

Actually, as far as using any APFSDS sabot types from a gun mortar, I really see no point: any given caliber (60mm, 81mm, 120mm) can carry a reasonably effective enough HEAT or HEDP for dealing with light & medium AFVs within direct fire ranges (<2km?).

Otherwise, high-angle pitch 'em to do the top attack thing, where armor is thinner and minimal ERA exists. A MRSI of even 60mm shells arcing into any known MBT's roof, HEAT or HEDP in origin (multipurpose like those subminitions in cluster bombs) or even an EFP warhead, would bust any known MBT just as an A-10's barrage of 30mm shells can do.

Singly, one shell of a medium caliber is nothing. En masse, bye bye MBT.

But then again, the system I envision is only for anti tank use as a last resort.

Hey, I like the idea of a Chaffee style turret.
A 75 with adequate enough anti armor performance if needed, and plenty of punch for general support work.

But I'd still prefer the gun mortar's high elevation advantage, allowing attacks over walls, buildings, and other obstructions or terrain features, without having to expose the entire vehicle for direct line of sight attacks for every shot (such as an MGS must do every time).

Of course, a Chaffee sized turret on top of a BFV hull would be a very tall vehicle, which has both pluses and minuses.

Minuses because against other AFVs, you stick out like a big sore thumb, having such a high silhouette and all.

Pluses because it gives the vehicle's commander a slightly higher perspective to view the battlefield from (height advantage here), as well as being able to fire over a majority of nearby vehicles (and possibly other obstructions and embankments and whatnot) at a lower angle & higher velocity.

The Bradley itself is already a tall vehicle (even moreso with its TOW launcher raised into firing position, and that new commander's independent viewer on the ODS models.

Also having seen a Chaffee before, its turret (as is, no redesign) wouldn't add any additional height that the Bradley doesn't have now.

But it would definitely look awkward as all hell, even if effective.

Still, a 75/76mm armed turret certainly would add some impressive teeth those insurgents would soon learn to respect/steer clear off, although it could also make the vehicle a primary target.

YelliChink,

any chance you have anything comparing the lengths & physical profiles of the 76mm L23 ammo to that of the MCB 81?

I have the 1985-86 Jane's Armour & Artillery laying around here, and it discusses the ammo for the MCB81 on pp 729-730, and suggests the mcb81 can fire not only the F811 APFSDS round, but also all Thomson Brandt 81mm mortar bombs.

A picture of the F811 shows it to be encased in, yes, a cartridge, that almost appears to be comprised of a (semi-combustible?) cloth type or mesh material that looks somewhat like the perforated casing of recoilless rifle ammunition.

A picture of a long range 81mm mortar projectile next to it shows, like typical mortar rounds, 8 charge increments clipped onto the bomb's tail, just forward of the fins (wheras the F811 has the appearance of a standard fixed ammunition, fully enclosed with its cartridge/case).

In the same JA&A, pp 805 & 806 list 81mm gun mortar turrets from both GIAT (CL81 weapon) and Thomson Brandt (MCB81 weapon), and pp 806-808 list 60mm gun mortar turrets and mounts from Hispano Suiza (Serval turret w/ 20mm & 7.5 or 7.62MG, and Mangouste turret w/ 12.7mm MG),

a Creusot-Loire system mounted behind a simple shield and having a very short barrel,

and a Thomson Brandt system in a surround shield and mounted in a special semi-circular cradle allowing side slope or hull cant compensations up to 12º. All the 60s allow muzzle loading also, but all the bombs appear to be standard configuration: there are no pictured nor discussed higher velocity APFSDS types for the 60mm.

As is done with the Russian 82mm Vasilyek mortar, automatic loading on any of these could make for ideal saturation weapons.

Were I specifically partial to 3" weapons, if I wanted high velocities, I'd opt for the ARES gun with its short cased telescopic ammo, as is used now with the 40mm CTAI gun.

Various installs of the ARES were reported to fire as fast as 90rpm (bursts, as limited magazine capacity wouldn't allow a full 90 rounds to be fired).

Could we envision a shorter barreled fire support howitzer utilizing the same encased am

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YelliChink 12/30/2006 2:02:26 AM

any chance you have anything comparing the lengths & physical profiles of the 76mm L23 ammo to that of the MCB 81?

Unfortunately, I don't have as much info on these systems as you do. My best guess is that if they have similar projectile weight and muzzle velocity, they should be roughly the same size.

A gun-mortar turrent needs its mount pivot inside the turrent ring so that high elevation angle can be achieved. If my memory serves me correct, AMOS follows this rule. BFV's hull must be radically redesigned to cope with AMOS or other gun mortar installment. CV90 is designed to be multi-purpose carrier. They've even put a 120mm tank cannon on it.

It is really a pleasure to debate with you, dogtagg. I actually learned a lot from your reply.

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doggtag 12/30/2006 4:33:00 AM

Actually, no.
Without risking any OpSec viloations,

anyone who's been inside a BFV (general public can typically get inside during defense expos and military parades or exhibits, such as recruiting events at the local county fair) would realize that the hull itself is more than adequate- it's the turret that needs some major redesign to accomodate anything other than a Chain Gun.

The BFV's turret would need a massive redesign to accomodate an AMOS or NEMO type system

(like I mentioned earlier: remove all the TOW- and Chain Gun- related hardware, and you'll free up a considerable amount of room: half the turret's internal volume is taken up by the TOW & 25mm systems), but the turret ring's diameter should be adequate enough (can't say I ever thought to measure across any of the ones we pulled turrets from).

I actually looked at it a little more closely the other day at work.

The biggest concern I'd have would be: how far into the crew compartment of the turret would the breech of a gun mortar, or any large gun (60-90mm), protrude,

and could the crew swing around the ammo from a stowage rack and index it inline with the breech?

An encased shell greater than a foot and a half long would be too difficult within the turret's current dimensions (as it sits with the current weapons system hardware).

Even the loader in an MBT has to work on his coordination so he can quickly load the proper ammo under combat-intense operations: there's not a lot of elbow room between him taking a round from the magazine, normally flipping it 180º end over end (vertical rotation), and loading it into the breech.

But certainly, a round such as an 81mm mortar bomb, with its charges stacked onto the bomb's tail forward of the fins, should be much more easily manipulated in the cramped confines of a turret than many of the longer (standard lay out) high pressure gun ammo, such the 60mm hypervelocity, the 76mm M32 series, or any of the Belgian CMI 90mm guns.

I have tons of pics from both online and books of various gun, mortar, and cannon/howitzer ammo, but very few of them list physical dimensions other than weight, and their muzzle velocities and ranges.

Sometimes, the best I can do is extrapolate from knowledge I have in handling rounds like the US 20mm & 25mm series in the past, and making my best guesstimate from there...

There's an Army Navy surplus store back in my hometown that has a couple of inert encased US 90mm tank rounds (metal only, no filler...I have no idea what gun they were for, or what their designation numbers are) that have been sitting in the store since as long as I can remember (2+ decades). I can definitely say, I wouldn't want to have to manhandle such rounds within a turret the size a Bradley has.

I remember one of the firstWar Memorial Expos I ever went to, ages ago (late 1970s?), and being inside an M3 Stuart. I remember the Coke-bottle sized dummy rounds they had stowed (anyone who remembers the 1970s can remember those glass soda pop bottles that got 10¢ when you returned them), and the fact that they could fairly easily be hand loaded, even in the confines of the little (compared to modern tanks) Stuart.

(the good old days, when turrets where so much less complex.)

...and it's certainly been a pleasure for me to debate with you on the subject as well ( keeps me out of trouble elsewhere).

That's what makes this forum so great.

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FSV 12/30/2006 7:20:44 AM

YelliChink:

"Now, back on French MCB-81 again. The crew have to learn three different kinds of gunnery: mortar, howitzer and tank cannon." Actually there are 2 types of Gunnery Techniques involved ...... Direct Lay Fire & Indirect Lay Fire techniques. My crews on the M48A3 & M60A1 tanks didn’t really have any problem learning or using both techniques. Direct Lay Fire is the quickest method for putting rounds on target.

As for turbulence.... anything moving through the air creates turbulence. Actually a blunt edge object creates more turbulence than a sharp edged object, while moving through the air. Properly designed & manufactured fins greatly reduce the turbulence created, as well as controlling its adverse effects on the flight of the projectile.

After reviewing your posts, I think that you may be confused about the purpose/use of gun-mortars. For a given caliber, firing HE, mortar ammunition is normally the cheapest ammunition. For a given caliber, a gun-mortar weighs far less & has great deal less recoil load than a high velocity cannon or howitzer. A gun-mortar is also easier & cheaper to manufacture.

Tho a gun-mortar can fire an APFSDS-T projectile, its penetration performance doesn’t even come close to the penetration performance of an APFSDS-T projectile fired from a high velocity tank cannon of the same caliber (which uses a heaver penetrator), at any range. An gun-mortar HEAT projectile will have a greater penetration capability (due to thinner projectile walls/more explosive filler) than a HEAT projectile fired from a same caliber high velocity cannon. But the high velocity cannon HEAT projectile will have a longer effective range (due to its velocity), against moving targets. As you can see, the gun-mortar has a limited anti-armor capability.

Where the gun-mortar really comes to the forefront is firing HE. Even when fired at a ‘low angle’ (less the 45 degrees) it has a far better (shape & size) casualty producing pattern than an HE projectile fired from a high or medium velocity cannons. A problem that ‘flat trajectory’ weapons have is killing enemy grunts when they are in foxholes/ditches/etc, or hiding behind walls/dikes/boulders/etc. With the high arching trajectory of the gun-mortar HE, I can drop the projectiles right on top of them and quicky chop them up into dog food.

The French gun-mortar weapons used a Split-Breechblock & don’t need a cartridge case to help seal the rear of the chamber area/volume. With mortars, the chamber area/volume varies, depending on the model of ammo being fired. In a mortar the bore walls are parallel to each other all the way to the Breech Cap/Plug. So the chamber area/volume is determined by the distance from the face of the breech cap to what ever provides rear obturation (sealing) for the projectile body, at the moment of firing. So chamber volume can be increased by just increasing the length of the projectile’s Tail Boom. Take a look in Jane’s Ammunition. In the Mortar Ammo Section. You’ll find that some mortars can fire 2 types of HE, Standard & Long Range. You’ll notice that the Long Range projectiles have a longer tail boom. This moves the fins back further so they will be better positioned in the super-sonic air flow and increases the chamber volume so more propellent can be used.

R/S Jake

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FSV 12/30/2006 7:44:35 AM

doggtag: Here is some data for you;

81mm Mortar ammo, fired from the M252:

High Explosive; M889A1: Weight = 4.18 kg Range = 5,900 m MV = 305 m/s Explosive = 0.93kg of Comp B Length = 49.96 cm (19.67 in) Casualty Radius = 40m lg X 30 m wide

Red Phosphorus; M819: Length = 64.0 cm (25.2 in) Weight = 4.9 kg M/V = 274 m/s Filler = 1.2 kg of RP

Illumination; M853A1: Length = 64.59 cm (25.43 in) Weight = 4 kg MV = 311 m/s

IR Illumination; M816: Length = 64.7 cm (25.49 in) Weight = 4.2 kg (9.25 lb)

76.2 mm for L23 & L23A1 cannon: (cartridge base is about 90-95 mm dia)

HE-T HEP-T Illumination
Length
Round 527 mm 539 mm 588 mm

Projectile 334 mm

Weight

Round 7.3 kg 7.42 kg 9.7 kg

Projectile 5.4 kg 5.4 kg 8 kg

Filling 0.6 kg Comp-B 0.6 kg Comp-B 700 g

Propellant 570 g 610 g 269.3 g

Fuze PI/PD Sq/Del BI/BD ET/PD

M.V. 514 m/s 533 m/s &nbs

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Herald1234 Keep it coming, guys, I'm getting educated! 12/30/2006 1:16:07 PM

and thank you!

Herald

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doggtag Great work you guys 12/30/2006 5:08:57 PM

See, now this is the stuff that keeps good threads going.

Thanks again booku much, Jake.

(how's the FSV concept going, by the way?)

I also wonder from time to time: would a modern day 25-pdr gun have merit?

Rumor has it there were still several of them in operation in brushfire wars up thru the 1990s.

Seems there's so much debate about "should everyone replace their lightweight, less lethal 105mm artillery with lightweight 155mm systems?"

But few people are looking at the obvious gap like I recently mentioned:

a majority of (western) nations embrace machine gun grenade launchers and autocannons up thru 40mm,

but then, except for those few 50-60mm and 81mm class mortars, they jump suddenly to 105mm howitzers, or even 120mm mortars, and up to 155mm, even if the overall logistics of supporting those major caliber tubes becomes expensive and physically cumbersome.

The Russians and all their client states kept 85mm guns in service for a considerable amount of time: these offered easier manhandling than most larger weapons, and yet still had capable potential against any non-MBT AFVs if the threat came about (but I'm not really pushing for a medium caliber armor killer).

And seeing how several nations have embraced various 90mm guns (French & Belgian developments, mostly),

one wonders where Germany could've advanced theeir famed and feared "88" if they had decided to bring it back as a Cold War weapon (APFSDS from an L71 88 could've been on par with early L7/M68 performance).

But looking at German experience with assault guns, we saw numerous examples (mostly StuG) with 75 & 105mm howitzers.

Britain used various Churchill, Cromwell, and similar chassis to mount 75mm, 25-pdr, and 95mm howitzers.

The US either had the 75 or 105, in anything from a halftrack to a tank chassis

(75mm M8 HMC on the Stuart and 105mm M37 on the Chaffee being my faves).

I like the gun mortar primarily for the mortar part: very high elevation allowing lobbing shells over obstructions, even if just a couple buildings to get a round or two a couple streets over. Try doing that with a howitzer.

But then I like the gun howitzer for the fact it offers better kinetic effect thru higher velocities for direct fire, which is my guess the reasoning behind the MGS and its 105mm M68-derived gun.

But since fire support is my primary thought in this thread,

would a Bradley hull be better served with a 120mm system (after reading the TankNet thread I posted up, I agree with their general consensus that a single barrel, manually loaded weapon would be better than an automated AMOS twin),

a 105mm howitzer (that would give us a rough equivalent of the Russian M1974 122mm SP gun),

or an 81mm gun mortar with a larger ammo supply?

Since long range isn't what I'm thinking (don't want them playing long range SP artillery: their role should be close range support),

I don't see a need to reach any farther than any of the surface-fired ATGMs (spotters would allow me to engage them outside their range, as well as many mortars that current forces in Iraq and A-stan are being harassed by- ranges estimated to be well under 10km).

If the US itself, and others, seem poised to adopt programmable airburst ammo in a number of light calibers (25mm ACSW/OCSW, 30mm Mauser in Puma AFV, 40mm in CV90, etc),

then I think the high angle capable gun mortar gives us a reasonable enough option (a prefragmented 81mm mortar round with a smart fuze could be programmed to work either as direct fire or high-angle).

And I'll also agree about the lower velocity tubes relying on HEAT or HEDP for any antiarmor work: ages ago, I've mentioned that rifle grenade called the RAAM, Rifleman's Anti Armor Munition, roughly the size of a WW2 Bazooka round, with the reported penetration of just over 400mm (16 inches). That should be able to be fabricated inside an 81mm mortar shell. Anything needing more than 16 inches of penetraion by our FSV shouldn't be engaged by our FSV in the first place (and it's highly doubtful any adversary MBTs would get through our other assets anyway... but if they did, firing our anti armor round high-angle for a top attack should silence him (if I don't have any dedicated anti armor assets nearby).

And as the Brits experienced with their Scorpion 76mm, a HESH/HEP round should be doable in 81mm also (be a hell of a way to make a roof entry hole), especially as its high angle descent would give it somewhat of a gravity assist to make sure it doesn't ricochet

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