M741 / m731 / m692 155-mm

[jvollenberg]

M741 / M731 / M692 155-MM Cargo projectiles.

Does anyone have pictures of these items? This is another group of items we are missing good pictures of and we are reworking the EOD publication.


Joe

 

[US-Subs]

Joe,
Its been a really long day and I'm beat - save me some time and tell me which projos these are - ?

 

[jvollenberg]

They are the Adam filled 155MM projectiles. We only have really bad angle shots of them (look like they came out of some old slide show). We are also looking for the RAMM filled ones as well. Although from my living room and without my publications at hand I don't know which those were.

There is no rush for these pics, can't do anything with them for a few day or sometime into next week anyways.

Joe

 

[US-Subs]

Yeah, I've got the ADAMs L and the RAMs S, I'll take some photos this weekend. Feeling better after a few hours sleep.

 

[US-Subs]

Here you go. Unfortunately my marked projos are currently without baseplates. I've got the RAAMs next to an umarked RAAMs with base for comparison. The unmarked M864 is there for no extra charge.

 

[jvollenberg]

Those will work great ... thanks.

Joe

 

[HAZORD]

Those are some fantastic looking projos!

 

[BOMBSaway1980]

What is the measurement for the base plates for the Projectiles

 

[BOMBSaway1980]

sorry RAAMS & ADAMS

 

[Sprockets]

M741/ m731/ m692 155-mm

Can anyone help concerning the details of the ejection sequence for the M692/ 731 Carrier Shell with ADAM submunitions? This shell would appear to have come from nowhere, as there are no U.S patents relating to it-Perhaps it originated in Europe? As I imagine it to be one of the first US sub-munition shells, there is surprisingly little information available. The desire to reduce all non-essential weight led to the front and rear portions being aluminium, with a very thin case wall. A lightweight glass fibre overwrap (Surprisingly a patent not yet found!) helped to sustain the radially directed centrifugal force exerted by the sector-shaped mines. Perhaps the desire to protect this overwrap from hot-gas exposure was the reason for the Plastic Obturator. The concept of the Central battery Activation Rod was foreshadowed in the US patent 2454281 (Yr.1945), where the time delay fuzes(Acid erosion of a wire) fitted to a stack of disc AP mines were activated by a rod passing through the stack, as also in the British "Ranger" Dispersed mines. Patent US 3665857 (Yr 1970) covered the so-called Fusible Closure used to lift shells in storage, and vent in the event of a fire.. Having such a thin wall, and possibly with a black-powder expelling charge, would perhaps have made this proj. particularly vulnerable to rapid "cook-off" in the event of a depot fire?
A)- As the shell had such a thin wall, the usual internal groove,ensuring that the contents revolved in harmony with the shell, could not be used. Perhaps the plastic spacers might be glued (Increasing the required expelling force, as well as making assembly even more difficult), or perhaps there were rubber end pads to ensure that friction rotated the stack initially, as the pie-shaped items would tend to wedge against the walls, once revolving.

B)-The "Ordata" attachment shows the expelling charge (Black Powder?) contained in a thin sleeve, surrounded by a thicker sleeve, which could possibly move axially. This would ensure an initial rapid rate of burning, but there are no holes in the thick sleeve for the gases to escape, after the inner case ruptured. Perhaps the outer sleeve moved axially, to open a valve? Any one know? See query E as an alternative scenario.

C)- The movement of the Battery Operation Rod is a puzzle. It must operate before the mines move, and there is a Piston carried loosely by the Pusher Plate. However, the Rod cannot move, as it is firmly set against the base (Perhaps the end portion collapses or buckles?), and there is clearance between the front end of the rod and the Piston. Drop testing the proj would shift this rod , unless it is anchored at, say the central Support Shelf? I can only imagine that the piston , with it's waisted portion, is designed to collapse axially, so moving the rod, after the end clearance is absorbed?

D)-Anyone ever see one being packed-quite an achievement?! Perhaps half the stack would be loosely erected, joints in alternate rows staggered. The Battery O.R. and the Support Shelf dropped on top, the bottom stack closed up around said rod and strapped, and the top set of mines added. As the case was lowered, the retaining straps would be removed, there being a lead-in to the casing.

E)-Surprisingly, there appears to be no Seal Ring around the Pusher Plate, as is now used. It looks as if perhaps my comment in B) is answered by the Thick Outer sleeve moving over the inner sleeve, and pushing the Pusher Plate via the Piston, which was designed to collapse initially to allow the Battery Rod to move, the Pusher Plate only moving after full Piston Collapse. So what appears to be an air space between the Spotting Charge and the Piston could either be a cushion, or else a solid steel anvil. Nowadays the gases tend to enter the whole head, which possibly demands a heavier Ogive, but is much less traumatic for the contents! If this was the true modus operandi, then there would have been quite a loud warning report overhead, though as the pressure would be released while the Subs were still in the shell, it was probably muffled. It would demand very solid Submunitions (ADAM was solid!, and there was no delicate parachute), as the expulsion was achieved with a short strong push, as opposed to today's gentler sustained push with pressure over the whole Pusher. I believe that certain Carrier Shells even prevented full expulsion of the Pusher Plate, so preventing the warning report, so a lower altitude could be used.

F)-Are Carrier Shells generally grouped into weight classes still?


Phew. Anyone out there who knows some of the answers?

Regards,
Martin.

 

[HAZORD]

I worked as a Machine Tool Engineer at one of the factories where the M483 projectiles were manufactured in 1989. At one time during peak production, they made approximately 24,000 projectiles a month. We forged and machined the aluminum Ogives and base plates, and forged, ironed, machined, and fiberglass wrapped the central body. The fiberglass was then ground to final projo diameter. We shipped complete projectiles and baseplates (minus cargo), 8 projos per pallet. Our projectiles were painted OD by a robotic paint line, first preheated in an oven, then primed with one automatic gun, and then OD painted with the second gun. There was a waterfall behind the projectiles as they were painted, to pull the fumes and overspray away. The projectiles would get their yellow cargo lettering and diamond markings when they were Arsenal loaded with their specific cargos.

The shipping ring for these projectiles has a central lead core, that is intended to melt out at high temperature, so that the expulsion charge doesn't eject the cargo if the projectiles are subject to high temperatures.


The same projectile body (Originally M483) was used for RAAM's, ADAM's, and the M42 grenades as an M483, and other experimental cargos. The pusher plate does indeed have an "O" ring around its outer diameter, just like a hydraulic cylinder. The aluminum ogive forging was the same for all rounds (It had an "O-ring") seal that was leak tested on every projectile. The aluminum bases differed from ADAMS to RAAMS to 483's. The BZ projectile had a steel base plate. There is a dovetail groove about 1/2 inch wide and 1/8 inch deep machined lengthwise into the inner bore of the projectile to prevent cargo rotation. The 8 inch equivalent M509 projectile has at 2 dovetail grooves machined down the length of the internal bore. There are aluminum wedges that engage the groove on one side and wedge between the M42 grenades on the other to prevent cargo rotation. Each wedge is the length of one M42 grenade, so each layer of grenades has its own wedge.

The M483 family of projectiles are not really thin walled. The SADARM projectile on the other hand is extremely thin walled as the SADARM submunitions are so large in diameter. The wall thickness is only about 1/8 inch on a SADARM, which couldn't sustain a crimped on rotating band, so the rotating band is mounted on the baseplate. Since the SADARMs are so thin, they are extremely hard to final machine and keep round. A machining nightmare.

 

[US-Subs]

The shipping ring for these projectiles has a central lead core, that is intended to melt out at high temperature, so that the expulsion charge doesn't eject the cargo if the projectiles are subject to high temperatures.

It is interesting that this does not always work in practice. I know one of the EOD units that had dozens of pallets of these (inert fill) and other projectiles, which they had set up as a mini ASP for training ops. One one occasion a couple of junior troops were sent out to perform area clean-up. Instead of weedwhackers, they elected to burn the grass off the area. The grass started the pallets burning, the rounds heated up, the sealed bodies then "popped" launching the body a short distance up, just far enough to dump the inert M42s. The ribbons and plastic tabs then burned - an interesting mess once the ashes cooled.

 

[HAZORD]

That doesn't surprise me. It takes around 800 degrees F. to melt the lead for bullets. That is pretty hot for a black powder expulsion charge.

All of the new U.S. Mortar rounds have a plastic sleeve between the metal mortar body and the fuze, so that the plastic will melt and release the fuze from the body in case of high heat.

 

[Sprockets]

Thanks, Hazord & US-Subs for your interesting comments.

The fact that the black-powder still managed to eject the contents seems to show that the fusible plug shipping ring would only work reliably with a detonating explosive, which would only perform if heated under pressure. If the thermal expansion pressure was relieved, then it might burn only.

Regarding Hazord's V.I comments about manufacturing the proj, as an engineer I found them really interesting. So despite the wall thickness (Or lack of it), wedges were used. Were dovetail grooves employed with SADARM, in which case I expect most machinists had heart attacks! Also, how were these grooves machined-Was an elongated planing tool used, or a small unit head carrying a dovetail mill traversed inside the bore?

I hate to do battle with Hazord, who worked on the actual proj, but I still feel that the carrier shell used for ADAM used a different launch system to that used later. There is no trace of an O-ring on the Pusher Plate, and it would be useless anyway , as the plate is at the head of the dovetail grooves. It does look as if the black-powder charge was contained in the thick-walled cylinder, and give a massive initial launching thrust, possibly cushioned slightly by a buffer. Later systems did use direct gas pressure on the Pusher, which would probably have a skirt moving in a grooveless part of the bore. Since the large volume of the head chamber would need to be filled, the charge would be contained in a perforated sleeve,containing a rupturable sleeve. Thus the black-powder would be pressurised to ensure rapid burning, after which ruptire would take place. If there was no initial containment, I imagine that an unacceptable delay might take place before expulsion, and any small leakage around the O-ring would be serious.

The point you made about grooves being used, Hazord, would negate the reduced noise-impact that could be achieved by preventing the Pusher from exiting, unless it was limited to a very short stroke short of the commencement of the grooves. Was this noise considered serious, or was high level operation used to reduce the signature at ground level?

Martin.

 

[US-Subs]

I don't think I've ever seen a dovetail used with any ejecting round, the possibility of binding would be pretty high. I know that the RAMs were a straight slot, I think the SADARM as well. Dont have the projo but I can check my different sadarms and see what they have on the body. I've got a cutaway of the ADAM projo, but never paid any attention to the ejection process, not relevant to anything I had to do with the projo or subs - either it was a full projo or the subs were out.

In regard to the 483s, it was my understanding that there was no ejection charge installed, it was just a buildup of pressure in the sealed projo once it got hot.

 

[HAZORD]

I have SADARM projectiles, and they don't have an internal groove. I have dummy SADARM 8 inch bodies and they fit into the 509 projectiles that have double grooves. I've never see a carrier projectile that tried to capture the pusher plate. That would require a ridge around the rear of the projectile which would hinder the ejection. The projectiles are loaded from the rear, given an appropriate number of thin plastic shims to complete the cargo length, and then the baseplate is screwed on to hold everything in place.

 

[weberoed]

M 692/731
IDENTIFICATION. The M 692 and M731 projectile differs only in markings and payload.
a. (U) Type. These are howitzer-fired, high-explosive (HE), separate-loaded, area denial artillery munitions (ADAM) containing base-ejected antipersonnel (apers) mines.
b. (U) Painting and Markings.
(1) (U) The projectiles are painted olive drab with markings stenciled in yellow.
(2) (U) The olive-drab letters L and S stenciled in the yellow triangles on the ogives of the M692 and M731 projectiles represent the self-destruct time for the mines within the projectiles.

DESCRIPTION.
a. (U) Material. The body is steel; the ogive and base are aluminum; the rotating band is copper; and the obturator is plastic. The center section of the body is wrapped with fiberglass.


b. (U) Weight. The fuzed projectile with payload weighs approximately 46.5 kilograms (102.5 pounds).

HAZARDOUS COMPONENTS. Each projectile contains a 51-gram (1.8-ounce) single-base propellant expelling charge and 36 mines. Each mine contains a 21-gram main charge of composition A-5 explosive and numerous small explosive components each weighing less than 1 gram.

FUNCTIONING. Initiation of the expelling charge generates pressure which drives the piston and battery-activation rod rearward, displacing the battery-activation ball and simultaneously shearing the detonator shorting bar on the mines. This initiates the arming sequence of the mines. The pressure generated by the expelling charge also drives the pusher plate rearward, shearing the projectile base threads and expelling the mines from the base. The spin of the projectile radically dispenses the mines as each layer emerges. The spotting charge provides a black puff marker when the pusher plate is ejected.



M 741

IDENTIFICATION. The M718,M718A1, M741 and M741A1 projectiles are externally identical except for markings.
a. (U) Type. These are separate-loaded projectiles containing base-ejected, ferromagnetic-influence-fired, antitank (AT) mines. All mines in each projectile incorporate a self-destruct feature; some mines in each projectile also incorporate an antidisturbance feature. The self-destruct time is 48 hours for the mines in the
M718 and M718A1 projectiles, and 4 hours for the mines in the M741 and M741A1 projectiles. The projectiles are fired from howitzers to deny or delay access to a particular area for a specific time period. The projectiles bear the acronym RAAMS,for Remote Anti-Armor Mine System.
b. (U) Painting and Markings. The projectiles are painted olive drab with yellow-stenciled identification and manufacturing markings and eight yellow triangles around the ogive as shown in figure 1. The letter L is stenciled in olive drab on the triangles of the M718 and M718A1 projectiles to denote a long self-destruct delay time for its mines. The letter S is similarly stenciled on the triangles of the M741 and M741A1 projectiles to denote a short self-destruct time for its mines.

DESCRIPTION.
a. (U) Material. The projectile bodies are steel and the ogives and baseplugs are aluminum. The rotating bands are copper and the obturators are plastic. The center section of each projectile body is wrapped with fiberglass.
b. (U) Weight. The fuzed projectiles weigh approximately 103.00 pounds (46.72 kilograms) each.

HAZARDOUS COMPONENTS. Each projectile contains a 51-gram (1.8-ounce) single-base propellant expelling charge and nine mines.

FUNCTIONING. Before the projectile is fired, the fuze is set to function during flight. On projectile firing, setback and centrifugal force initiate functioning of the fuze and partially arm the mines. When the fuze functions, it initiates the expelling charge, which creates pressure on the pusher plate. The pusher plate drives the mines rearward, shearing the baseplug threads and ejecting the mines from the projectile body. If the projectile fuze fails to function, the mines may complete their arming sequence on projectile impact, and proceed to function in their intended manner.

I think there was a comment about black powder being used in these, maybe in early models but even back in my day I don't remember BP being used, rather a single based propellant. Don't think this description and drawings show the spacers very well though

 

[HAZORD]

The dovetail on the groove is very slight. It isn't like the dovetail holding rear sights on a firearm.

 

[Sprockets]

Hazord,
When I mentioned that the Pusher Plate is retained, one way is to have an expanding snap-ring engage with a groove. i couldn;t find the exact reference, but a French firm just let the pusher move just enough to shear the bottom closure threads, and then stop. gas was then bled through a central hole in the Pusher, so as to continue movement of the cargo. This was part of a complicated method to stop the piston striking the last cargo on exit-Cords even used! This wouldn't reduce the opening report, though.

I am amazed the Sadarm shell did not have a groove-Perhaps they were relying on tight axial clamping? You state that replica Sadarm bodies fit into another shell-body, provided with twin grooves. Thinking about it, only cargo in segments could use grooves, as they have gaps to take the wedges. Thus large diameter mines, unless having projections themselves, would not have packing wedges. Probably they were made a very accurate fit, but it is surprising that they rotated in one with the shell!
Your point about short wedges makes sense when the separate layers of wedge shaped munitions break joint, like brickwork.
Interesting about the shallow dovetail-Was it actually undercut, or did it have the widest dimension on the inside of the shell?

Machining the grooves-Was I correct in thinking that a small vertical milling cutter was moved on an overhung rail inside the proj. body?
It is interesting that they have not shown an-O-ring on both the variations shown by weberoed-it just shows how you cannot trust dwgs entirely! However, I would have thought that if grooves were provided, as with the ADAM (pie-shaped) items,then the O-rings could not seal, and also would be torn to shreds. Perhaps O-rings were only used for grooveless projs, which would apply to all shell-I.D. munitions?
If you look at the weberoed dwgs, the proj on the right would require the aluminium cylinder, possibly plastic lined, containing the expelling charge to rupture. (Strange that there is no spotting charge-surely both would need this?) The other proj for the ADAM munition has quite a different construction, perhaps because the grooves prevented a seal being made. Once the end was forced free, a much lower force would suffice to continue piston movement-The piston would have exited the front cylinder, and gases would act directly on the leaky expelling piston. Do you have acess to a detailed sketch of this portion of the shell?

Thanks,

Martin.

 

[Sprockets]

Thanks, US-Subs,

How does the RAAM cylindrical mine fit the groove/s, as there is no room for a wedge, unlike a segmental munition? I would really appreciate it if you could check your detailed ADAM dispenser and see if the expelling plate does have an O-ring groove, that the piston can partially collapse to move the battery rod before moving the expelling plate, and that there is clearance between the battery rod far end and the base. Also, is the battery rod secured by a shearable connection to the central rest plate, to stop it shifting during drop testing. It is strange that only the ADAM unit has a spotting charge?

When they discard their cargo, do they have a distinctive noise signature, warning those below to take cover?

Finally, interesting that it was air pressure alone that caused the expulsion of the training munitions-The projectiles were well sealed then!
Many thanks,
Martin Cummins.
It is strange that there is no