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3/20/2017 5:03:23 PM
Posted: 7/17/2001 5:46:33 PM EDT
Ok guys, I'm wondering how a mortar works. What happens between the time the round is dropped down the tube and the time it leaves the tube. Thanks
Link Posted: 7/17/2001 5:53:16 PM EDT
Link Posted: 7/17/2001 5:55:32 PM EDT
When the round is dropped down the tube, it slides relatively slowly toward the bottom because of the air trapped under it. When it reaches the bottom of the closed tube, it hits a fixed firing pin. A large primer is set-off that ignites powder charges wrapped around the tail of the mortar round. The expanding gases then push the round out of the tube and off to the target.
Link Posted: 7/17/2001 6:15:27 PM EDT
Is it a propellant in the rocketry sense or in the firearms sense? If the former, does it continue to burn after leaving the tube? In dem movies, the mortars always go "whoomp," not bang. Thanks guys for humoring my ignorance.
Link Posted: 7/17/2001 6:24:20 PM EDT
It is a similar type propellent to firearms rather than a rocket. There have been rocket assisted mortar rounds tested, but I don't know if any are in use. As a side note the motar can also be breech loaded and fired by pulling a lanyard just like other types of artillery. Most are the drop down the throat type, because it's the simplest, cheapest, and most reliable, but the very large mortars have to be breech loaded because of the size/weight of the round and the length of the tube makes it impractical to load from the muzzle. Oh, and mortars are generally smoothbore. Mortars are basically small, shortbarrel, very high trajectory artillery pieces. The high trajectory limits range, but gives you good indirect fire angles (i.e. shooting over obstacles and from behind cover) useful at the short ranges that they are employed. Ross
Link Posted: 7/17/2001 6:27:21 PM EDT
Originally Posted By david_r: Is it a propellant in the rocketry sense or in the firearms sense?
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NOT ROCKETRY!!!!!!!!!!!!!!! Rockets utilize a timed, internal payload to generate thrust. Mortars use combustion. Not like Gyrojets. Gyrojets. I had one of those once [:(]
Link Posted: 7/17/2001 6:40:34 PM EDT
Also, most mortars are smooth bore, the rounds stabalized by their fins. Their have been rifled mortars, however, most notably the US 4.2in which had a concave plate of copper between the propellant section and the body of the round. When the propellant fired this flattened out both sealing the propellant gas behind it and gripping the rifling. For many years this was the longest ranged and most accurate mortar in the world. A few small mortars also have triggers. The British 2in and 51mm mortars, and the 60mm Israeli Soltam/US M224 mortars have trigers and firing pins that can be cocked and trigger fired- the firing pin being recocked by the firing. Or it can be fixed in the uncocked position and the rounds drop fired. This dual mode alows the mortars to be carried loaded, and also a limited degree of low angle fire. Mortars have become awsome pieces of destructive firepower. The M224 can fire 30rpm using charges 0 and 1 forever, without overheating.
Link Posted: 7/17/2001 6:42:40 PM EDT
Tell me if I'm getting this. There is a propellant wrapped around the base of the mortar shell that is detonated with a primer. The area below the body inside the tube is in effect the casing. Thus, looking at a fired round it would be missing the propellant housing as there isn't one to begin with, just some propellant glommed on. Is that close?
Link Posted: 7/17/2001 7:13:11 PM EDT
The M224 can do 30 RPMs for 4 minutes, after that you go to the sustained rate of 20 RPMs. Rifled mortars are much more accurate than the fin stabilized because of the effects of wind on the fin. This combined with the fact that most mortar sections will not have a met that covers the lines of met that they are firing through ensure mediocre accuracy at extended ranges with fin stabilized rounds. David R Yes, very close, the primer itself is charge zero and has a little more power than a blank shotgun round. The extra charges are either tied on clipped on C-charges. Sometimes in wet conditions you will get incomplete burns and occasionally you will see things like unburned charges fall off the mortar bombs in flight. Around the body of the mortar bombs there are ductile gas checks that expand to prevent most propellant blow by (this is actually one of the ways to ID caliber of the mortar round after it has functioned, since different caliber rounds have different sized gas checks find a piece of frag that was once the part of the gas check and you can ID the round).
Link Posted: 7/17/2001 7:23:02 PM EDT
The M224 can do 30 RPMs for 4 minutes, after that you go to the sustained rate of 20 RPMs. Oops, the FAS left that last little part off of their webpage.
Link Posted: 7/17/2001 8:21:08 PM EDT
Link Posted: 7/17/2001 11:18:17 PM EDT
Link Posted: 7/17/2001 11:19:49 PM EDT
Link Posted: 7/17/2001 11:24:39 PM EDT
Link Posted: 7/17/2001 11:27:12 PM EDT
Link Posted: 7/18/2001 3:28:38 AM EDT
One the picture of the M252 and the M224 you can see the "C" charges on the stem of the mortar rounds, on TP and HE rounds respectively. For obvious reason they are refereed to as donuts. This is the pub that explain mortars [url]http://155.217.58.58/cgi-bin/atdl.dll/fm/23-90/toc.htm[/url] This pub explains mortar gunnery [url]http://155.217.58.58/cgi-bin/atdl.dll/fm/23-91/toc.htm[/url]
Link Posted: 7/18/2001 4:49:43 AM EDT
[Last Edit: 7/18/2001 4:46:45 AM EDT by Stg44]
Unlike most movies and TV, when a mortar fires, it makes a loud WHAM. I worked with the 4 deuce, or 4.2" mortar extensively. It was awsome in the hands of a good crew. I was running range safety on our mortar platoons ARTEP while with 1st Cav. They had one exercise called a hip shoot. The old M106 gasser (essentially an M113 with a turntable and accordion doors insted of the normal hatch on top of the crew compartment, and a gas instea of diesiel engine) lined up with the aiming stakes, range estimated, and a round fired. 1st round, direct hit. They lost points because they didn't bracket the target, an old PC. To give you an idea of how loud a mortar going off is, while in the desert doing searchlight for a crunchie (infantry) live fire, the signal to turn on the searchlight was the sound of the mortar going off. The 81mm's were firing flares, and when you were using the xenon searchlight, you had to be revved up to about 1200 rpm. We were about 1/4 mile away from the mortars, engine on a M48A5 revved up, CVC helment on, and could clearly hear the mortar tube go over all that noise. Pucker Factor 101-have a misfire on a mortar. Watch the range officer as the tube is lowered, and the round-which some were not spin armed at the time I was in, slide down the tube into his hands. One oops, and you are blown to bits.
Link Posted: 7/18/2001 5:56:00 AM EDT
Stg44, I think they were exaggerating the danger in removing misfires from a mortar tube. The fuses in US mortar projectiles are designed so that they do not arm until they are well out of the tube. The fin-stabilized projectiles (60mm and 81mm) have a setback pin, which withdraws on firing and allows an out of line detonator to move into firing position. This movement is retarded by an escapement mechanism, which allows the delayed arming. In some of the older fuzes a jump out pin in the fuze body is retained by the tube wall until in clears the tube. (90% of the dud 60mm and 81mm rounds I worked on still had this pin in place.) The pin is released by the setback in firing. All this is not to say that due care should not be used. Anything made by the lowest bidder can fail.
Link Posted: 7/18/2001 6:11:11 AM EDT
Mortar is: Cement Sand Lime water
Link Posted: 7/18/2001 6:18:16 AM EDT
EOD Guy, I was referring to the 4 deuce round. I know they all hated a misfire with a passion. Lots of the ammo they were using was Korean War era. I hung some WP for shitz and giggles, made in '53. We had a crew burn up in a M106-going from range where they had been firing flares. Excess propellant, (they called it cheese cake as I recall) went off, set off 50 or so flares, couple of hundred gallons of gas...the track was melted flat when it finally went out. This was before my personal hero, Ronald Regan spent some bucks on bringing us up from the years of decline after Vietnam, and Carter.
Link Posted: 7/18/2001 6:43:25 AM EDT
[Last Edit: 7/18/2001 6:42:43 AM EDT by shari71]
Here's my mortar, it fires a Pringles can full of Plaster of Paris, with a capful of black powder @45 degrees it will go 100 yards. With more powder, or a flatter trajectory it will go farther, but it's longer to walk to get it. [img]http://home.adelphia.net/~langralls/mortar.jpg[/img]
Link Posted: 7/18/2001 7:03:32 AM EDT
Originally Posted By DK-Prof: Another thing that might not have been made completely clear (forgive me if it was and I'm just rambling).... The reason for the charges being something that you add on, and not just part of the round, is that you can add different numbers, and thus get different ranges with the same weapon. If you always just needed the same amount of propellant, there would be no point in adding it seperately - but the flexibility is what makes it such a neat idea. Also remember that a mortar in essence works oppositely from the long gun you are used to - in a long gun you raise the trajectory towards 45% to get maximum range, in a mortar you lower the trajectory towards 45% to get maximum range. Usually mortar shells (or the few I'm familiar with - 60mm and 90mm) also don't arm themselves until they have left the tube - even after you have pulled the safety pin from the grenade. My impression is that it is often some sort of inertial arming, meaning that it has to be traveling at a relatively high speed to arm itself. Always encouraging to know when someone drops a shell on its impact fuse after pulling the pin out.
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Are you refering to 45 Deg's from a 90 deg angle?
Link Posted: 7/18/2001 7:18:15 AM EDT
Link Posted: 7/18/2001 2:14:59 PM EDT
Mortars are designed to shoot high angle, above 800 mils. However, some breech loading mortars LAV 120, can be used for low angle "assault" fire to attack point targets. Guns (either artillery pieces, naval guns and tanks) fire high velocity, flat trajectory, but they can still shoot high angle in some cases, it not the preferred method and with tanks you must build an inclined ramp in order for them to elevate high enough for high angle. Howitzer can fire either low angle or high angle (Max EL on US 155 mm howitzers are 1275 mils). They use a variable charge system to partly allow customization of velocity to range and angle of fire/fall. EOD: The fear for clearing mortar misfires is not so much one of a fuze function. There are 2 big concerns, the primer has lit and is a slow cooking on that can go off, with enough velocity to penetrate a human body (I have seen fingers and parts of the hand removed by 81s firing lower charges), or hit a solid object and cause fuze function. The second and most often occurring, the gas checks have got hung up on fouling within the tube. Movement of the tube shakes the round loose causing the round to complete its journey, striking the firing pin and launch out the tube. There was has been at least 1 mounted M30 4.2 mortar destroyed when this has happened and the round left the tube hitting the interior of the track causing its fuze to function. The M252, has an easy to removable firing pin just for this occasion.
Link Posted: 7/18/2001 2:28:53 PM EDT
A few years back, there was a brewing controversy: It was determined that mortar-men were suffering from slight hearing loss, as an obvious and unfortunate by-product of their jobs. NOSHA, lawyers, activists all whined and whined that these men needed adequate hearing protection. Of course, adequate hearing protection meant that the men could no longer hear commands. Our reply was that a little hearing damage was nothing, compare to the possible damage resulting from not hearing "SHORT ROUND!!!!". We won. My hearing ain't what it used to be.
Link Posted: 7/18/2001 2:40:13 PM EDT
Maj Murphy Were you in when the still had the M29? I never heard on of them fire the closest I can think of is a M252 without a BAD. When it is on, about 2/3 of the muzzle blast is diverted into the air. You can defiantly hear the difference between a M252 with and without the BAD. Too bad that that force causes too much baseplate slip so they couldn't put one on the M224 if it was using the assault baseplate.
Link Posted: 7/18/2001 2:43:18 PM EDT
STLRN, I got booted from those links you posted for not having the proper ID. [:)] CS
Link Posted: 7/18/2001 3:46:14 PM EDT
That is funny may just be an ISP thing. I can get those pubs from my home system without any problem. Try going to [url]http://155.217.58.58/rtddltextv.html[/url], under the search criteria enter FMs and infantry. You will see quite a few other pubs on their, the ones with keys are restricted access pubs, look for the FM 23-90, 23-91 and the FM 7-90. They all deal with mortars.
Link Posted: 7/18/2001 3:51:29 PM EDT
STLRN, I was enlisted (0311) '86--90. Commissioned '90-'96 (active). Regretfully, as an LT, I never had the pleasure of leading a Weapons Plt, only Rifle Plts, XO.
Link Posted: 7/18/2001 7:32:06 PM EDT
[Last Edit: 7/18/2001 7:53:00 PM EDT by ArmdLbrl]
Oh my goodness STLRN I was right. [url]http://155.217.58.58/cgi-bin/atdl.dll/fm/23-90/ch3.htm[/url] Check Table 3-1 At 0 and 1 there really is no limit to how long you can fire the M224 at 30rpm. That makes the handheld version a REALLY nasty piece of firepower. Its a awsome gureillia/raiding weapon, think of what it would do to parked planes, or to a police station, or other such target on a hit and run. Of course, how long would it be before you wore the crews out, not to mention they would need a truck to carry the ammo needed. Edited to get the @#$%& link to work
Link Posted: 7/18/2001 8:13:21 PM EDT
Originally Posted By ArmdLbrl: Oh my goodness STLRN I was right. [url]http://155.217.58.58/cgi-bin/atdl.dll/fm/23-90/ch3.htm[/url] Check Table 3-1 At 0 and 1 there really is no limit to how long you can fire the M224 at 30rpm. That makes the handheld version a REALLY nasty piece of firepower. Its a awsome gureillia/raiding weapon, think of what it would do to parked planes, or to a police station, or other such target on a hit and run. Of course, how long would it be before you wore the crews out, not to mention they would need a truck to carry the ammo needed. Edited to get the @#$%& link to work
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Oh here we go another school shooting! [:D]
Link Posted: 7/18/2001 8:16:30 PM EDT
is what they did in Saving Private Ryan possible? When they slammed the mortar shell on a piece of metal and threw it like a grenade.
Link Posted: 7/18/2001 8:25:22 PM EDT
I dont think the new fuses will do that, no. But that really did happen a couple times in WWII so obviously you can do that with the old WWII era ammo. Not sure about the second series of 60mm ammo we introduced between Korea and Vietnam for the M19. Any Nam vets know?
Link Posted: 7/18/2001 8:25:27 PM EDT
EODGUY Are you looking for employment, we hire EOD techs to do UXO removal and avoidance. If you are interested contact me via e-mail I will send you some information. Jim Beam
Link Posted: 7/19/2001 2:36:24 AM EDT
ArmdLbrl The reason it says it there is no limit is that the ROF goes way down in the hand held mode, it will takes more than 3-4 seconds per round. In the bipod mode, all you do is check the sights and drop the round. In the hand held mode, you drop the round, align the range indicator on the handle (or eye ball it) and pull the trigger (you actually aim after you load, vice before). It takes a lot longer, than the 2 seconds for the drop mode. With that firing sequence it is hard to even get to 20 RPMs. Hence below the sustained rate of the weapon. The 30 RPM rate is because if the A gunner is the only one loading, it takes about 2 seconds per round. However, if the highly discouraged practice of double loading occurs, both a-gunner and another gunner loads, you can shoot around 45-50 rounds in the first minute, if a dropped round doesn't catch a fired round on its way out.
Link Posted: 7/19/2001 6:58:07 AM EDT
The moment I read the title of this thread, I was disappointed to see our friend andreusan wasnt the author :( M.
Link Posted: 7/19/2001 9:21:15 AM EDT
I always laugh when I hear the sound of morters on movies and TV shows. You can rest assured that they are quite "f"ing loud when they go off. I used to stuff my inboard ear with something and poke my finger in the other as the round was sliding down the tube. On 81's you could tell if a round was going short the second it fired by the sound, usually giving ample time to run like hell. Not as easy to tell with the 60 but it had to come alot closer for the shrapnel to still be hot enought to burn you. BTW if I remember correctly, the propellent charges on 81s looked like little sandbags and the charges on the 60 looked flat squares of yellow plastic covered in clear plastic held on by clips. What are those doughnut rings on the body of those 60 shells? Beankeeper 0341
Link Posted: 7/19/2001 12:52:26 PM EDT
Beankeeper You been out a while if that is the type of ammo you remember, those rounds are classified type "B" ammunition and to be used for training and fired in combat only as a last resort. They don't have anywhere near the lethality or range of the newer rounds.
Link Posted: 7/19/2001 12:56:26 PM EDT
However, if the highly discouraged practice of double loading occurs, both a-gunner and another gunner loads, you can shoot around 45-50 rounds in the first minute, if a dropped round doesn't catch a fired round on its way out.
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Ouch!...[grenade]
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