120mm mortar - which country developed it?

[Mattias]

<BLOCKQUOTE>quote:</font><HR>Originally posted by JasonC:

It is possible the 82mm was really the same size, since the original Brandt was 3.2 inches = 81.3mm. Maybe some rounded that down, and the Russians rounded it up. I've heard the story that they deliberately made them 1mm larger for the sake of the captured ammo difference, many times from many sources, but it is vaguely possible it could be a common but apocryphal story.<HR></BLOCKQUOTE>

Jason,

Gander/Chamberlain (Enzyklopädie Deutscher Waffen) also lists the Soviet mortar as having a calibre of 82 mm, as opposed to the 81,4 mm of the Gr.W. 34 (called 8 cm by the Germans).

It would be very interesting to see if the calibre/ammunition issue indeed is some kind of popular misconception. Tell if you find anything out..

M.

[Monty's Double]

Wasn't the 77mm the designation given to the cut down version of the 17 pounder used on the Comet (reduced propellant charge and shorter breech I think)? Does anyone still care?

[Jarmo]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Michael Dorosh:

Acutally, I may be confusing another piece of German or Russian ordnance - there was something used in WW II that was given a different mm size solely for logistical reasons. <HR></BLOCKQUOTE>

That rings a bell, but damn if I remember what it was.

Could it be the 75 vs 76 mm ammo?

[Juardis]

wow, great stuff guys. Thanks a bunch. One more question though. Wouldn't machining the ordnance change the flight characteristics such that they would be less accurate? I guess if the explosion is big enough, who cares, but in the case of AP rounds, accuracy is everything.

[ASL Veteran]

Just one minor comment. According to Ian Hogg (not me), the role of the 50mm mortar was replaced by the addition of a rifle grenade launcher in German squads. However, I can certainly accept that maybe a combination of both the rifle grenade and the 81mm was used to fill the void from the withdrawal of the 50mm from service.

[Guest Babra]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Juardis:

Wouldn't machining the ordnance change the flight characteristics such that they would be less accurate?<HR></BLOCKQUOTE>

Lathes are standard machine shop items, even in the field. Assuming any machining was necessary for the mortar rounds in question, they would only have to be turned down to a depth of 1/2 a millimetre. This would definitely affect blast and fragmentation (for good or ill I wouldn't care to say), and would probably somewhat affect trajectory (again, it might even improve it), but I doubt it would be crucial either way.

Anyway, that whole line of argument is based on supposition. I'm just saying it's possible if necessary. I'm not aware of any documentary evidence to support the notion that it was done.

[WWB]

Am I the only one who thinks putting live mortar shells on a lave is a fundamentally bad idea?

WWB

[Guest Babra]

<BLOCKQUOTE>quote:</font><HR>Originally posted by wwb_99:

Am I the only one who thinks putting live mortar shells on a lave is a fundamentally bad idea?

<HR></BLOCKQUOTE>

Uh... They do come apart. It's possible to unpack and repack them.

[argie]

<BLOCKQUOTE>quote:</font><HR>Originally posted by JasonC:

"I think the 77mm gun"

Yes, that is another good example. Several guns were designated "77mm" in this country or that, when in fact no weapon of that caliber was used, by anyone. It was a quarter-master's designation. But one does not find such a practice, unless their is something to confuse the renamed shell size with, a different type of the same caliber.

It is possible the 82mm was really the same size, since the original Brandt was 3.2 inches = 81.3mm. Maybe some rounded that down, and the Russians rounded it up. I've heard the story that they deliberately made them 1mm larger for the sake of the captured ammo difference, many times from many sources, but it is vaguely possible it could be a common but apocryphal story.

[ 05-09-2001: Message edited by: JasonC ]<HR></BLOCKQUOTE>

I'm having an "anal" attack

The correct figure for the original Brandt is 81.4mm... Today mortars in many countries still uses that caliber.

[JasonC]

"the original Brandt is 81.4mm"

LOL - yes, you are right of course. Serves me right for using an approximation and still putting in another significant digit.

I got 81.3 by the following approximation - 3.2 inches, and 12.7mm is a .50 cal which is half an inch, so 6.4 x 12.7 = 81.28 ~ 81.3. And it is, too. It is just that the Brandt wasn't 3.2 inches (3.2047 - LOL).

[JasonC]

"in the case of AP rounds, accuracy is everything."

Mortars are notoriously innaccurate. Which doesn't matter too much for the HE mission, since you want some spread of the "beaten zone". But to give you an example, the Germans developed an 81mm HEAT round to try to attack the top armor of tanks. It was quickly realized mortars are far, far too innaccurate for this to be a useful idea.

With the 81mm, they expected around half of the shells to land within around 30 meters of the aim point, and half to land outside. In practice, the rule was to watch the fall of shot, and if you got 1 round within 50 meters of the target, or one over and another under, to fire for effect on that setting immediately.

So basically they assumed a ~50 meter accuracy was about as good as they would get in practice, and then let the random fall of the rounds plaster the area. Since the shells would fall in a random scatter-graph around the aim point anyway.

This is very different from high velocity, flat-trajectory guns, where the "scatter" was around a meter or so even a 1 km ranges, and almost all the "miss" was because of aim not being exactly right (including range estimates).

In contrast to such weapons, mortars are low velocity, are not rifled (a few exceptions - e.g. U.S. 4.2" was), have a long hang time, spin and wobble in flight, and have greater "windage" between round size and bore size. Slight changes in round size would probably make a difference yes, but much smaller than the existing causes of scatter, so it would just be lost in the existing "noise".

Incidentally, CM seems to use the same system for both types of guns in the case of on-map mortars, and probably makes them too accurate as a result. Though I think a patch toned this down somewhat. In particular, the size to side-to-side error for on-map mortars is essentially nil in CM, when in practice is was more like ~1/2 the size of the range error. Which is more like the CM indirect fire system, than the on-map one.

Incidentally, just as a piece of military trivia, there have been tech developments of some mortars in very recent times that could overcome the ordinary innaccuracy of mortars. Terminally IR guided 120mm HEAT rounds have been developed, both in the US, and by Bofors. Which potentially make heavy mortars a serious threat to tanks, in a way they never have been in the past, simply because they couldn't hit them.

[offtaskagain]

<BLOCKQUOTE>quote:</font><HR>Originally posted by JasonC:

[QB

Incidentally, just as a piece of military trivia, there have been tech developments of some mortars in very recent times that could overcome the ordinary innaccuracy of mortars. Terminally IR guided 120mm HEAT rounds have been developed, both in the US, and by Bofors. Which potentially make heavy mortars a serious threat to tanks, in a way they never have been in the past, simply because they couldn't hit them.[/QB]<HR></BLOCKQUOTE>

There is also the Copperhead laser guided 155mm round. Good for tanks and bunkers, but they are rather expensive. There weren't that many made, but it would be cool to have in a modern day CM.

[JasonC]

"There is also the Copperhead laser guided 155mm round. Good for tanks and bunkers, but they are rather expensive."

True.

Unit cost of the 120mm "smart" HEAT mortar rounds is on the order of $40,000. In tests they get about 50% hits against tank targets, and a hit is at least a mobility kill. A bargain of a trade any way you cut it, it seems to me. Also, it uses any standard 120mm mortar, with little addition crew training required. Just the round and a sight-like attachment to the mortar itself.

[Username]

Theres also a glide option in the works. The mortor shell springs out wings at the top of its flight. It then becomes a glide bomb extending its range. It would have the laser designator also.

This would be great for light forces that have to get big bang for the weight.

[Olle Petersson]

<BLOCKQUOTE>quote:</font><HR>Originally posted by JasonC:

Mortars are notoriously innaccurate.<HR></BLOCKQUOTE>From what I've heard the first German 12cm mortars were notoriously accurate!

It's no good having all shells from a mortar land within the crater of the first shell... <BLOCKQUOTE>quote:</font><HR>there have been tech developments of some mortars in very recent times that could overcome the ordinary innaccuracy of mortars. Terminally IR guided 120mm HEAT rounds have been developed, both in the US, and by Bofors.<HR></BLOCKQUOTE>The Bofors system is called Strix and is currently in service with the Swedish army. It's supposed to be used many-on-many, i.e. lots of rounds fired at a concentration (company up) of armour. The IR seeker is supposed to recognise the difference between "live" and knocked out vehicles, aiming for the former. It's a tandem HEAT warhead attacking at a very steep angle.

The Bofors also has the BONUS project, current state unknown to me. It's a 155mm AT round with two warheads in each shell. Also IR seeking and designed to be used as IF many-on-many. These warheads have lesser penetration than the Strix though.

Cheers

Olle

[JasonC]

"From what I've heard the first German 12cm mortars were notoriously accurate"

The CEP is 65 meters - larger than for smaller mortars BTW. Half within that, half without. It is artillery. In CM, on map mortars hit like directly-laid, flat trajectory field guns. They should use the indirect fire routine like for off-map artillery, but they don't. So you see every mortar round land on an except line for the mortar, range error only. That did not happen.