How does a mortar work?

[WimpBastard]

http://www.96th-infantry-division.com/decorations/moh.htm

He displayed conspicuous gallantry and intrepidity above and beyond the call of duty. When a powerfully conducted predawn Japanese counterattack struck his unit's flank, he ordered his men to take cover in an old tomb, and then, armed only with a carbine, faced the onslaught alone. After emptying 1 magazine at pointblank range into the screaming attackers, he seized an enemy mortar dud and threw it back among the charging Japs, killing several as it burst. Securing a box of mortar shells, he extracted the safety pins, banged the bases upon a rock to arm them and proceeded alternately to hurl shells and fire his piece among the fanatical foe, finally forcing them to withdraw. Despite the protests of his comrades, and bleeding profusely from a severe shrapnel wound, he made his way to his company commander to report the action. T/Sgt. Anderson's intrepid conduct in the face of overwhelming odds accounted for 25 enemy killed and several machineguns and knee mortars destroyed, thus single-handedly removing a serious threat to the company's flank.

I also found http://www.worldwar1.com/dbc/smortar.htm quite interesting

There were some instances reported of Doughboys using mortar shells by removing the safety pin and then throwing them in the manner of large hand grenades. Due to the power of the 3" mortar shell as compared to a hand grenade, this practice, while effective at times, was fraught with danger.

I'd guess the fact that the mortar is being armed on a rock would mean the propellant would "harmlessly" discharge outwards in all directions rather than forcing a mortar round out a tube.

[cmfan]

Hmmm... I guess you do learn something new everyday.

I suppose I don't really doubt the veracity of the medal of honor write up -- but still, there's something strange about it.

"he seized an enemy mortar dud and threw it back among the charging Japs, killing several as it burst" -- why throw a dud? Duds aren't exactly safe, they sometimes explode unexpectedly, but you can't count on them to do so either.

"his piece" -- slightly unmilitary like slang

Apart from these items I noticed that he was throwing rounds from a "knee mortar". This type of mortar used a 45mm round I believe -- might have to check on that. It did not have a bipod and its rather small baseplate was integrated into the tube. The name "knee mortar" is a misnomer as placing it on your knee to fire it would result in a broken leg. It required the operator to pull a langyard attached to the firing pin in order to fire a round.

----

"I'd guess the fact that the mortar is being armed on a rock would mean the propellant would "harmlessly" discharge outwards in all directions rather than forcing a mortar round out a tube."

True, but the "propellant" is an expanding, burning, hot gas. If you ignite it while holding the round, it will likely burn your hand pretty badly.

One thing I forgot to mention is that in all the mortar rounds I've handled, the striking cap has been slightly recessed into the base. I suppose this *might* prevent the ignition charge from going of if you slamed it against a rock or baseplate, but you're takinga big gamble. I suppose in combat if your desperate its worth the chance. Still... I stand by my claim that what we saw in SPR was somewhat of a stretch.

[Liddell-Hart]

Didn't Robert Cain win a VC at Arnhem for (among other things) taking on tanks single handedly with a two inch mortar aimed on an almost flat trajectory?, I haven't a clue how he managed it but I've definitely read it.

[Michael Emrys]

The 2" mortar was specifically designed so that it could be fired horizontally, or at least nearly so. AIUI, the round is not fired gravitationally as in other mortars, but has a spring loaded firing pin like other types of firearms. This made it more useful in house to house fighting as it could be fired into windows and other openings in walls. It's interesting to note that this role has been taken over by today's grenade launchers.

Michael

[Michael Emrys]

And interesting page on British mortars, including the 2", can be found here.

Michael

[athkatla]

I would suspect that the 'banging a mortar round on a rock to arm it' applies to the 2" mortar, NOT the 81mm mortar. I, like cmfan, am not absolutely sure about this, (I've been out the Army 21 years now, and besides, I wasn't that good on ammo characteristics on my course), but I believe that the 81mm round only arms when a certain height is reached, due to, IIRC, some kind of ball bearings slipping into place inside the round when it reaches a certain height, and setting off a chain reaction that results in arming the round. I'm sorry if this is a bit vague, but I never kept my manuals on leaving the Army, and the memory is a bit the worse for wear now.

Edited to include a useful link. Scroll down the page to view the Fuzes section for info about delayed arming of the fuze.

Click Here

[ November 23, 2004, 06:00 AM: Message edited by: athkatla ]

[JonS]

Originally posted by cmfan:

One factor you do have to watch out for though is counter battery radar -- don't think this existed during WWII.

It did. Brits and Canadians in 21st AG used it from Normandy onwards.

[athkatla]

Originally posted by JonS:

</font><blockquote>quote:</font><hr />Originally posted by cmfan:

One factor you do have to watch out for though is counter battery radar -- don't think this existed during WWII.

It did. Brits and Canadians in 21st AG used it from Normandy onwards. </font>

[cmfan]

very interesting reading material. thanks athkatla

[Splinty]

A few posts back someone wondered what it sounded like to be under a mortar attack. Having been mortared a few dozen times in Iraq, I can tell you that you don't hear any whistle or hiss at all. What you hear is the sound of the round launching from the tube, and we estimated most of what was aimed our way was launched from around 3 klicks out. These were Russian made 120mm's and you can imagine how loud the " thump" was to be heard from that far. Needless to say we all got very good at recognizing that sound.

[athkatla]

Originally posted by Splinty:

A few posts back someone wondered what it sounded like to be under a mortar attack. Having been mortared a few dozen times in Iraq, I can tell you that you don't hear any whistle or hiss at all. What you hear is the sound of the round launching from the tube, and we estimated most of what was aimed our way was launched from around 3 klicks out. These were Russian made 120mm's and you can imagine how loud the " thump" was to be heard from that far. Needless to say we all got very good at recognizing that sound.

Nice to hear you survived those attacks, I've never been under a mortar barrage, but have several times heard the crack of a high calibre round passing over my head, and back in the 70's the slow thump of a Thompson being fired wildly at my position. Luckily, same as you, no blood was spilt on those occassions, not mine anyway!

[mitchum]

You can definitly hear the mortar rounds coming, but not soon enough to do anything about it

http://www.militaryvideos.net/torrents/mortar_attack_in_a-stan.mpg.torrent

That is a torrent of a mortar attack in afghanistan, and you can hear em.

[Denwad]

Audie Murphy also used mortar round ( I believe 60mm ) as handgrenades

[Folbec]

Originally posted by WimpBastard:

[QB] http://www.96th-infantry-division.com/decorations/moh.htm

</font><blockquote>quote:</font><hr />After emptying 1 magazine at pointblank range into the screaming attackers, he seized an enemy mortar dud and threw it back among the charging Japs, killing several as it burst.

</font>

[Tarquelne]

The following morning the enemy attack was resumed. Cpl. Kelly took a position at an open window of the storehouse. One machine gunner had been killed at this position and several other soldiers wounded. Cpl. Kelly delivered continuous aimed and effective fire upon the enemy with his automatic rifle until the weapon locked from overheating. Finding another automatic rifle, he again directed effective fire upon the enemy until this weapon also locked. At this critical point, with the enemy threatening to overrun the position, Cpl. Kelly picked up 60-mm. mortar shells, pulled the safety pins, and used the shells as grenades, killing at least 5 of the enemy.

Safety pins?

Anyway, he was at the storehouse because he'd run out of ammo from wandering around and eliminating enemy MG nests earlier. Sometimes those Rambo flicks don't seem all that far fetched:

MOH - Charles E. Kelly

[DavidMc]

Also of interest, I noticed that if you stand directly behind an 81mm mortar when fired, you can actually see the round for a couple of seconds as it goes up. Kind of fun to watch...

Having carried the baseplate of an 81mm for some distances, they are portable sort of...but I wouldn't want to have to hump that thing for miles on end.

Dave

B E A T N A V Y ! !

[ November 29, 2004, 03:58 PM: Message edited by: DavidMc ]

[cmfan]

When we use to fire the old 4.2 inch mortar at low charge you could easily spot the round flying through the air upto a good distance.

[jthomas]

Interestingly enough the same can be done with a 155mm Howitzer!

[Jeff Heidman]

ICBMs - you can see them for a bit after they are fired.

[McEvilly]

Started out on 81s in 1976, humped them everywhere. They are fun to do a direct lay with!

[kmart]

To extend and clairify on the reason for "banging" the bottom of the mortar in SPR; not all mortars are the same, but light mortars of the type depicted had the following features:

-A fuse at the tip designed to ignite the charge no matter what direction or velocity of impact (a haybale would still set it off)

-A safety pin, preventing the fuse from getting triggered if dropped.

-An internal safety that is triggered by the accelleration of the shell at launch.

The important thing to note is that banging metal against metal results in very high accelleration, if only for an instant, that is adequate for removing the internal safety.

The internal safety is there so that if you pull the pin, then drop the round, you don't kill your whole team.

So, in SPR, the trick of pulling the pin, arming (removing the internal safety by banging) then throwing it would have worked perfectly well. Due to the fact that there was no firing pin on the plate they were banging, the propellant wouldn't go off.

And yes:

-modern mortars don't work this way. Inertal triggers have replaced the accleration triggers.

-it is very dangerous to do this, but if your choice is to do this or get shot by 20 or so people, the choice is obvious.

-this wasn't the safest mortar design in the world, but many WWII weapons were not "safe". As Rummy says, you fight with the army you have, not what you wish you had.

[Dandelion]

Originally posted by kmart: To extend and clairify on the reason for "banging" the bottom of the mortar in SPR; not all mortars are the same, but light mortars of the type depicted [---]

What type is it that they depict in the SPR scene?

Cheerio

Dandelion

[0341-USMC]

I know this is kind of an old subject and thread but I had to laugh reading some of the comments by folks who have never seen a 60mm mortar let alone trained to fire one!

Obviously there aren't too many 60mm mortarmen left out there.

The 60mm mortar used in the private ryan movie was the same one we used in the marines in the 70's. Ours had a stamp right on the tube "US ARMY 1941" The only thing that changed was the date on the amunition and the sight box. Instead of a leather box (wwII) ours was aluminium but you never carried the sight in the box. The sight went in your pocket and your ciggaretts went in the box because it was waterproof. If you were lucky you had some beers to put in the tube. The 60mm HE rounds and all 60mm rounds have a primer in the base simular to a shotgun primer. This is your ignition charge that strikes the firing pin which "ALL" mortars had. This primer ignited the lanching charges which in the case of 60's were four small flat square increments clipped between the fins on the tail. You adjusted the range by removing the increments from charge 0 to charge 4 and then adjusted the elevation on the sight and the gun acording to the range card which was in every case of rounds. I have never seen nor heard of anyone using the rounds as impact grenades! When the round fired at the bottom of the tube a bore riding safety popped out of the side of the fuse and rode the inside of the tube until the round exited the muzzle and then flew clear of the round. Two feet after leaving the muzzle the round was armed and any impact on the plunger in the nose of the fuse would set it off. Some folks have identified the wire clip on the fuse as an arming wire. This is incorrect, it is a safety wire to prevent the plunger from being depressed. If you fire the round with the safety wire in it will not detonate.

Just my 2 cents worth.

[Michael Dorosh]

Originally posted by 0341-USMC:

I know this is kind of an old subject and thread but I had to laugh reading some of the comments by folks who have never seen a 60mm mortar let alone trained to fire one!

Obviously there aren't too many 60mm mortarmen left out there..

Every infantry platoon in the current Canadian Army uses the American M19 60mm Mortar; my own unit still has war dated muzzle covers for theirs.

Obviously you don't know as much as you might think about them...

60mm M19 CAN Light Mortar – a Work-a-Day Weapon for Indirect Fire Support

The M19 is a WWII-era mortar of US origin. Like all ‘small’ mortars, the 60mm M19 is serviced by a crew of two — one aiming with the dial sight while ‘number two’ drops the bomb down the tube. When the bomb’s primer strikes the firing pin in the bottom of the tube, the weapon fires. The system is so simple that a well-trained crew can maintain a rate of fire of 30 rounds per minute – although the sustained rate of fire is only 8 rounds per minute. While infantry is on the move, the M19 can be aimed by hand (right) using the lightweight M1 base-plate. For increased accuracy, M19s can be equipped with the more conventional M5 bipod mount and a C2A1 dial sight (left).

http://www.sfu.ca/casr/101-mortar60.htm

Page is down for review at present; above is the URL it used to be on; the google cache still works though.