25x137 ammo for Oerlikon KBA-BO2 and Bushmaster M242 chaingun

Cutaway models of some 25x137mm catridges. These cartridges are mainly used in the Oerlikon KBA-BO2 and the Bushmaster M242 chaingun Automatic cannon series.
This gun was based on the 25mm gun produced by the TRW company in the USA. The concept was designed in 1964 by Eugene stoner and used a rotating bolt lock. The weapon was meant for the Bushmaster trials, but the weapon was also extensively tested in Europe as the TRW 6425. When the Bushmaster project was postphoned due to the Vietnam war , Oerlikon took over the European patens rights for the gun.
Development and modifications took place; the weapon was changed from recoil operated to gas operated. It was the first weapon to have a dual feed sysytem incorperated , allowing it to change the ammo type High explosive to Armour piercing f.i.-.
The Oerlikon manufactured gun is known as the KBA-BO2, optimised for use in APCs, IFVs and scout vehicles. The Dutch YPR-PRI armoured personel carrier uses the KBA-BO2 gun in its GBI-A01 turrets.
The USA development ended up in the M242 Bushmaster chaingun. The term chaingun is derived from the use of a roller chain that drives the bolt back and forward. Unlike most automatic guns the M242 does not depend on gas operated recoil , it uses a 1.5 Hp (750 Watt) DC motor, positioned in the receiver to drive the chain and dual feed system. This system uses sprockets and extractor grooves to feed, load, fire, extract, and eject rounds. The M242 Bushmaster is for instance used on the M2 Bradley infantery fighting vehicle. More developments around this same cartridge are the French 25x137 Giat M811 gun, the Gau-12 Equilizer gatling gun (USA). The US navy uses the Gun as the Mk38 automatic gun. Cartridges for these guns are interchangable.


Pict. 01:
HE-T-SD (High explosive- Tracer- Self Destruct) of Dutch manufacture (EMZ / Eurometaal Zaandam). Type designation unknown. The fuze uses the disc type mechanical self destruct device (see drawing). Below this disc, a rolled up steel tape (like a serpentina roll) prevents the firing pin from moving down and froms the barrel safety; upon firing the centrifugal force unrolls the serpentina roll, enabeling the firing pin to pass. The centrifugal arming ball houses the firing cap, however the firing cap is set out of line with the firing pin. Only after firing the projectile, the centrifucal force rotates the ball in line with the centerline of the projectile and firing pin. The ball itself is fixed in itsafe position by a copper horseshoe (transport safety), clamped over a groove in the lower part of the ball. Only after firing , the centrifugal force bends open the horse shoe releasing the ball to rorate.

Pict. 02:
HEI- SD (High explosive Incendiary- Self Destruct). Cartridge of Swiss design and manufacture. It is meant to be used against soft skinned targets, helikopters, enemy personel and fire positions. The nose fuze has a mechanical self destruct mechanism.

Pict. 03:
HE-T M-DN-81 High Explosive Tracer type M-Dn 81. The cartridge is designed an produced by Diehl (Germany). The projectiel is of the Semi Armout piercing type, the reason why it has a base fuze. Above the explosive charge a pressed charge of zirconiumpowder is placed which acts as an incendiary charge.
The lower part of the fuze uses the disc type mechanical self destruct device (see pict). Above this, the delay mechanism is placed. This exists of a small aluminium bushing with small balls placed in it. If the bushing moves forward upon impact on the target the balls move outward into a groove, so delaying the spring loaded firing pin in its action. This bushing is kept axially fixated by a horse shoe shaped clamp that bends open through centrifugal force after firing, releasing the bushing to move. Above this mechanism, a rolled up steel tape (like a serpentina roll) prevents the firing pin from moving up and froms the barrel safety; upon firing the centrifugal force unrolls the serpentina roll, enabeling the firing pin to pass. The centrifugal arming ball houses the firing cap, however the firing cap is set out of line with the firing pin. Only after firing the projectile, the centrifucal force rotates the ball in line with the centerline of the projectile and firing pin. The ball itself is fixed in itsafe position by a copper horseshoe, clamped over a groove in the upper part of the ball. Only after firing, the centrifugal force bends open the horse shoe releasing the ball to rotate. A second ball safety exits of two pins, one radialy placed, retaining the ball, the second -axial- one blocks the radial one. Only after firing the set back force moves the axial pin down, releasing the radial pin to move outward, releasing the ball.

Pict. 04:
M792 HEI-T (High Explosive Incendiary Tracer). A cartridge of US origin. The projectile is filled with 32 grams of Hexal and fuzed with nose fuze M758with mechanical self destruct mechanism. It is meant to be used against soft skinned targets, helikopters, enemy personel and fire positions. V0: 1100 mtrs sec.

Pict. 05:
APFSDS-T (Armour Piercing Fin Stabilized Discarding Sabot Tracer), produced by Oerlikon. A tungsten cardide penetrator with an aluminium windshield, surrounded by plastic sabots and a plastic windshield. V0: 1440 mtrs/sec. Penetration: 36mm @60degr @1000 mtrs. , 31mm @60degr. @2000 mtrs.

Pict. 06:
APDS-T , (Armour Piercing Discarding Sabot- Tracer) made by Oerlikon. Dutch name: Ctg (cartridge) No.:113. A tungsten carbide core surrounded by plastic sabots. Vo: 1335 mtrs/sec. Penetration: 30mm @60 degr. @1000 mtrs., 25mm @60 degr. @2000 mtrs.

Pict. 07:
APDS-T (Armour Piercing Discarding Sabot- Tracer), produced by NWM. Instead of the black plastic sabots as used with the Oerlikon cartridge (06) this cartridge uses a straight body with hard nylon sabots. Penetration will be appoximately the same as the Oerlikon type (No.06).

Pict. 08:
TPDS (Target Practice Discarding Sabot. Practice APDS-T cartrige for medium ranges of Dutch manufacture (NWM).

Pict. 09:
TPDS (target Practice Discarding sabot), practice APDS-T cartrige for medium ranges of Dutch manufacture (EMZ). In the Dutch nomenclature: Ctg No.125.

Pict. 10:
Practice medium range Linked, cartridge No.127, practice APDS-T cartrige for medium ranges of Dutch manufacture (EMZ).

Pict. 11:
Sabot test. An experimental NWM projectile, supposedly to test the lower aluminium sabot.

Pict. 12:
TP-T (Target Practice Tracer) Ctg (cartridge) No.114, produced by EMZ. A steel projectile body, filled with inert resign. The dummy nosefuze is made of aluminium.

Pict. 13:
Break up. Short range practice with weapon functioning under full working pressure. A dutch invention. Exists of a thin plastic body, filled with steel powder. Shortly after leaving the barrel, centrifugal forces throw the steel powder outward, ripping open the plastic body. The plastic body remains and the steeldust drop to the ground at appr 10 to 20 mtrs before the barrel.

Pict. 14:
Unknown cartridge. Most probably a short range practice APFSDS projectile. Shellcase with EMZ base stamping

Pict. 15:
Blank cartridge. The body is made of black PVC, the base is made of brass. Stamped in base text: 02-BF-00. Country of origin unknown

Pict. 16:
Drill cartridge M86 B3. The lower part is a normal shellcase, the middle part is made of white nylon, the dummy fuze is made of aluminium. Country of origin unknown

Very nice, I like them a lot. Thanks for showing them.

Dave.

DJ,

An excellent display as usual! Thanks for sharing.

Thanks folks, my pleasure.
I got some extra info about No.14. It is a cartridge used by Dutch ammo factory's to test the quality of delivered powder for APFSDS-T cartridges. As one only had a short test range, these flat nosed projectiles were used.

No. 15 is said to be a Norwegian manufactured blank.

regards DJH

NIce as always,
Pic 1 was never used in the dutch army so designation unkwon,Pic 7 is the Nr 124 and pic 8 is Nr 289.

Thanks a lot for the info BLU, I will add the info in the other forums.
No 1 has a EMZ shellcase, so it was produced in Holland. The fuze however has this tyical German mechanical self destruct disc, so either the fuzes were bought in Germany, either some factory bought different parts (fuze , projectile body and shellcase) and assembled them.
However, the outside of the projectile cutaway has not been painted, as with all Oerlikon factory cutaway models in my collection.
I hope someone has a description and type designation of this cartridge.

Regards DJH

A rather interesting item I was able to obtain; a 25x137 Tubulair projectile. This is a Dutch experimental projectile designed and tested by the former NWM factories in ‘s Hertogenbosch. I suppose the thought was to make a projectile in the shape of a knive edged pipe to reduce the friction with the air. A base plug was glued in with heat dissolving glue, enshuring the base plug was kept in place during storage, handling and firing, and was blown off by the airstream after leaving the barrel.
Upon impact, the projectile would have cut through the target like a high speed apple corer (Apfelbohrer). It is not known what the ballistic test results were, or why the experiment was ended.
Regards, DJH

As my collection of 25x137 Oerlikon cartridges has expanded, here an update:

Pict. 01:
HE-T-SD (High explosive- Tracer- Self Destruct) of Dutch manufacture (EMZ / Eurometaal Zaandam). Type designation unknown. The fuze uses the “disc type” mechanical self destruct device (see drawing). Below this disc, a rolled up steel tape (like a serpentina roll) prevents the firing pin from moving down and forms the barrel safety; upon firing the centrifugal force unrolls the “serpentina roll, enabling the firing pin to pass. The centrifugal arming ball houses the firing cap, however the firing cap is set “out of line” with the firing pin. Only after firing the projectile, the centrifugal force rotates the ball in line with the centreline of the projectile and firing pin. The ball itself is fixed in it’safe position by a copper “horseshoe” (transport safety), clamped over a groove in the lower part of the ball. Only after firing , the centrifugal force bends open the “horse shoe” releasing the ball to rotate.

Pict. 02:
HEI- SD (High explosive Incendiary- Self Destruct). Cartridge of US design and Dutch manufacture. It is meant to be used against soft skinned targets, helicopters, enemy personnel and fire positions. The nose fuze has a mechanical self destruct mechanism.
The nose fuze is aluminium made. In the base of the fuze, the detonator is screwed. Above the detonator, the centrifugal arming ball houses the firing cap, however the firing cap is set “out of line” with the firing pin. Only after firing the projectile, the centrifucal force rotates the ball in line with the centerline of the projectile and firing pin. The ball itself is fixed in it’safe position by the spring loaded firing pin housing pressing upon a flat surface on top of the ball. Four balls are placed in radial drilled holes in the firing pin housing. Upon firing, the centrifugal force throws the balls outward, climbing up the chamfered wall on the inside of the fuze housing, releasing the rotor safey ball.
If a target is hit, the firing pin housing is hammered inward, forcing the four balls inward, pushing the firing pin into the firing cap in the rotor safety ball. If no target is hit, the velocity as well as rotation decrease, up till a moment where the force of the spring pushing the firing pin housing forward overcomes the force of the four balls in the groove (centrifugal force) and pushes the balls back inward and the firing pin backward into the firing cap. This is the mechanical self destruct mechanism of the projectile.


Pict. 03:
HEI- SD (High explosive Incendiary- Self Destruct). Cartridge of US design and Dutch manufacture. This particular cartridge is marked AI 69 (1969) and must be one of the first series manufactured by AI

Pict. 04:
Swiss manufactured HEI-T (High Explosive Incendiary Tracer) , Swiss name : SLB 050. Weight of the projectile : 180 grams. The projectile is filled with Hexal.
The nose fuze is aluminium made. In the base of the fuze, the detonator is screwed. Above the detonator, the centrifugal arming ball houses the firing cap, however the firing cap is set “out of line” with the firing pin. Only after firing the projectile, the centrifucal force rotates the ball in line with the centerline of the projectile and firing pin. The ball itself is fixated in it’safe position by a rolled up steel tape that inwinds after firing, releasing the rotor safety all . Four balls are placed in radial drilled holes in the firing pin housing. Upon firing, the centrifugal force throws the balls outward, climbing up the chamfered edge on the inside of the fuze housing.
If a target is hit, the firing pin housing is hammered inward, forcing the four balls inward, pushing the firing pin into the firing cap in the rotor safety ball. If no target is hit, the velocity as well as rotation decrease, up till a moment where the force of the spring pushing the firing pin housing forward overcomes the force of the four balls in the groove (centrifugal force) and pushes the balls back inward and the firing pin backward into the firing cap. This is the mechanical self destruct mechanism of the projectile.


Pict. 05:
US manufactured PGU-25 A/U & Mk210 Mod 2 Aerojet configuration HEI-T.
The projectile is fuzed with the M505A3 nose impact fuze. (also used on the 20x102 Vulcan HE cartridges)

The M505A3 nose impact fuze is made of seven parts:
-the steel fuze housing
-the detonator ball
-the U shaped red copper clamp (around the det. ball)
-the booster cap
-the collared firing pin
-the ballistic nose tip.
The detonator Ball has a channel, containing the detonator. In rest this channel is out of line with the firing pin so the firing pin cannot reach the detonator. A U shaped red copper calmp fixates the ball in this position.
On firing, the U shaped clamp is forced open by the centrifugal force, releasing the ball. The centrifugal force will now start to throw the heaviest part of the ball outward, thereby turning the detonator channel in line with the centerline of the projectile.
On impact, the ballistic cap is hammered inward, pushing the firing pin down (ripping it of the collar) into the detonator. This will set of the detonator, the booster (white) and the main charge.


Pict. 06/ 07:
M792 HEI-T (High Explosive Incendiary –Tracer). A cartridge of US origin. The projectile is filled with 32 grams of Hexal and fuzed with nose fuze M758with mechanical self destruct mechanism. It is meant to be used against soft skinned targets, helikopters, enemy personel and fire positions. V0: 1100 mtrs sec.

Pict. 08:
HE-T M-DN-81 High Explosive –Tracer type M-Dn 81. The cartridge is designed an produced by Diehl (Germany). The projectile is of the Semi Armour piercing type, the reason why it has a base fuze. Above the explosive charge a pressed charge of zirconium powder is placed which acts as an incendiary charge.
The lower part of the fuze uses the “disc type” mechanical self destruct device (see pict). Above this, the delay mechanism is placed. This exists of a small aluminium bushing with small balls placed in it. If the bushing moves forward upon impact on the target the balls move outward into a groove, so delaying the spring loaded firing pin in it’s action. This bushing is kept axially fixated by a horse shoe shaped clamp that bends open through centrifugal force after firing, releasing the bushing to move. Above this mechanism, a rolled up steel tape (like a serpentina roll) prevents the firing pin from moving up and forms the barrel safety; upon firing the centrifugal force unrolls the “serpentina roll, enabling the firing pin to pass. The centrifugal arming ball houses the firing cap, however the firing cap is set “out of line with the firing pin. Only after firing the projectile, the centrifugal force rotates the ball in line with the centreline of the projectile and firing pin. The ball itself is fixed in it’safe position by a copper “horseshoe”, clamped over a groove in the upper part of the ball. Only after firing, the centrifugal force bends open the “horse shoe” releasing the ball to rotate. A second ball safety exits of two pins, one radially placed, retaining the ball, the second -axial- one blocks the radial one. Only after firing the set back force moves the axial pin down, releasing the radial pin to move outward, releasing the ball.

Pict. 09:
Dutch manufactured APHE-T Cartridge No.112. The Swiss name of the projectile is : PLB. The projectile has a steel body with a hardened nose. On top of the nose piece an aluminium ballistic cap is placed. In the base of the projectile a base fuze is screwed. The projectile is filled with 10,7 grams of Hexal. The base fuze is named BZB 336. It is a delayed impact mechanical self destruct fuze. The fuze is aluminium made, with a tracer element crimped to the base. In top of the fuze, the detonator is screwed. Below the detonator, the centrifugal arming ball houses the firing cap, however the firing cap is set “out of line” with the firing pin. Only after firing the projectile, the centrifucal force rotates the ball in line with the centerline of the projectile and firing pin. The ball itself is fixed in it’safe position by a copper “horseshoe” (transport safety), clamped over a groove in the lower part of the ball. Only after firing , the centrifugal force bends open the “horse shoe” releasing the ball to rotate. Below that, a spring loaded firing pin is placed in a housing, kept in backward position by a rolled up steel tape (like a serpentina roll) which prevents the firing pin from moving forward so and forms the barrel safety; upon firing the centrifugal force unrolls the “serpentina roll, releasing the firing pin. The lower part of the firing pin housing has four radial holes drilled , in which a ball is placed. Upon firing, these balls are thrown outward and fall into a groove, locking the spring loaded firing pin housing in it’s backward position as the rolled up steel tape unwinds.
If a target is hit, the firing pin housing is swung forward by the inertia, forcing the four balls inward, pushing the firing pin into the firing cap in the arming ball. If no target is hit, the velocity as well as rotation decrease, up till a moment where the force of the spring pushing the firing pin housing forward overcomes the force of the four balls in the groove (centrifugal force) and pushes the balls back inward and the firing pin forward into the firing cap. This is the mechanical self destruct mechanism of the projectile.

The Cartridge No.112 will penetrate 10mm of steel at 1000 mtrs @30 degrees, and than explode inside the target.
Vo: 1100 mtrs./sec
Weight cartridge: 502 grams
Weight projectile: 180 grams

Pict. 10:
APHE-T Cartridge No.112. The Swiss name of the projectile is : PLB. This yellow painted projectile is for the pilot series of the Ctg. No.112. Service cartridges were later painted black.

Pict. 11:
M935A2 APFSDS-T. A tungsten finned arrow, surrounded by three aluminium sabots. After leaving the barrel, the transparent windshield breaks open, the sabots fall away and only the dart travels towards he target. It is stated to defeat a BMP-3 at 1500 mtrs.

Pict. 12:
APFSDS-T (Armour Piercing Fin Stabilized Discarding Sabot –Tracer), produced by Oerlikon. A tungsten cardide penetrator with an aluminium windshield, surrounded by plastic sabots and a plastic windshield. V0: 1440 mtrs/sec. Penetration: 36mm @60degr @1000 mtrs. , 31mm @60degr. @2000 mtrs.

Pict. 13:
M937 TP-T/DS (Target Practice-Tracer/Discarding Sabot). A practice APFSDS-T projectile. The cartridge is manufactured by Mecar Begium.

Pict. 14:
Swiss APDS (most probably experimental) with a single sabot. A black plastic cap is placed on top of the projectile. The tungsten penetrator has an aluminium ballistic cap and is held in position by a interrupted ring at the base that opens by rotation after firing. This releases the tungsten penetrator from the sabot.

Pict. 15:
Swiss APDS-T , (Armour Piercing Discarding Sabot- Tracer) made by Oerlikon. A tungsten carbide core surrounded by plastic sabots. Vo: 1335 mtrs/sec. Penetration: 30mm @60 degr. @1000 mtrs., 25mm @60 degr. @2000 mtrs.

Pict. 16:
APDS-T , (Armour Piercing Discarding Sabot- Tracer) made by Oerlikon. Dutch name: Ctg (cartridge) No.:113. A tungsten carbide core surrounded by plastic sabots. Penetration will be comparable with the Swiss APDS-T (Pict.15)

Pict. 17:
APDS-T (Armour Piercing Discarding Sabot- Tracer) Nr.124, produced by NWM. Instead of the black plastic sabots as used with the original Oerlikon designed cartridge (Pict.15) this cartridge uses a straight body with hard nylon sabots. Penetration will be comparable with the Swiss APDS-T (Pict.15)

Pict. 18:
TPDS (target Practice Discarding sabot), practice APDS-T cartridge for medium ranges of Dutch manufacture (EMZ). In the Dutch nomenclature: Ctg No.125.

Pict. 19:
TPDS (Target Practice Discarding Sabot) Nr.289. Practice APDS-T cartridge for medium ranges of Dutch manufacture (NWM).

Pict.20:
Practice medium range Linked, cartridge No.127, practice APDS-T cartridge for medium ranges of Dutch manufacture (EMZ).

Pict.21:
TP-T (Target Practice –Tracer) Ctg (cartridge) No.114, produced by EMZ. A steel projectile body, filled with inert resign. The dummy nose fuze is made of aluminium.

Pict.22:
M-793 TP-T cartridge of US origin. A mild steel body with a tracer element at the base. An aluminium dummy nose fuze is crimped in place.

Pict.23:
Dutch TP (Target Practice) manufactured by NWM. A steel body with an aluminium dummy fuze.

Pict.24:
Also a M-793 TP-T cartridge of US origin. A mild steel body with a hole drilled in top and base. In the base hole the tracer element is placed. Over the top a sheet aluminium windshield is placed. Apparently two different designs (both Pict.22 and Pict.24 are M793) can be called the same.

Pict.25:
Short Range –Tracer of German manufacture. A steel body, with a screwed in tracer element in the base. On top of the projectile a blue plastic cap is placed. Upon firing, gasses pass through a small hole in the tracer into the cavity in the projectile, pressing of the plastic nose piece. With the plastic nose piece gone, the blunt shape of the nose ensures short range..

Pict.26:
Short Range –Tracer and spotter of German manufacture. A steel body, with a tracer element in the base. On top of the projectile a bred plastic cap is placed. Upon firing, gasses pass through a small hole in the tracer, pressing of the plastic nose piece. With the plastic nose piece gone, the blunt shape of the nose ensures short range. Three .22 rimfire cartridges –at 120 degrees each- are placed in the top of the projectile body. Upon impact with the –cartboard- practice target the .22 rimfire cartridge is ignited. This gives a bright flash, which marks the point of impact.

Pict.27:
Break up. Short range practice projectile with the weapon functioning under full working pressure. A Dutch invention. Exists of a thin plastic body, filled with steel powder. Shortly after leaving the barrel, centrifugal forces throw the steel powder outward, ripping open the plastic body. The plastic body remains and the steel dust drop to the ground at appr 10 to 20 mtrs before the barrel.

Pict.28:
Swiss High Pressure test cartridge. He projectile has two extra wide plastic driving bands to ensure a gas tight travel through the barrel.

Pict.29:
Tubular projectile. This is a Dutch experimental projectile designed and tested by the former NWM factories in ‘s Hertogenbosch. I suppose the thought was to make a projectile in the shape of a knive edged pipe to reduce the friction with the air. A base plug was glued in with heat dissolving glue, enshuring the base plug was kept in place during storage, handling and firing, and was blown off by the airstream after leaving the barrel.
Upon impact, the projectile would have cut through the target like a high speed apple corer (Apfelbohrer).
I found the reason why the Tubular projectile does not propperly function while reading this booklet:

AFATL-TR-84-03, Historical Development Summary of Automatic Cannon Caliber Ammunition.: 20-30Millimeter
Author: Dale M Davis

"Tubular Projectiles:
The ability of a projectile to retain its launch velocity is a directfunction of the ballistic coefficient W/CdA, where W is the weight, Cd is a drag coefficient which results from shape and finish, and A is the crosssectional area of the projectile.
For at least the past 100 years, possibly as long as we have been firing spin stabilized projectiles, someone has periodically suggested drilling a hole axially
through the projectile to "let the air through" or, in practice, reduce the aross-sectional area. Another way of looking at it, even with modern knowledge, is that if 50%of a projectile's drag is nose drag and 40% is base drag, then eliminating much of the nose and base should significantly reduce drag. Over the years, this had been tried many times. Even as late as World War II, this was tried at BRLwith the 20 mm TP M99 projectile. It never worked as expected. The reason was quite simple. No one understood supersonic aerodynamics, especially supersonic flow through tubes. The flow would choke so that the flow through the tube was subsonic, much below the projectile velocity. The resulting drag was higher than it would have been had the projectile not been drilled.
The idea was'resurrected again in the 1970's. By this time, the Armament Laboratory had a good aeroballistic range and personnel knowledgeable in supersonic aerodynamics. In the mid-1970's, we ran a series of experiments by varying diameter ratios, nose and base angles, and area ratios in convergent and divergent nozzles. We were able to specify conditions under which supersonic flow could be established and maintained through the tube.
Many people and organizations became excited with this new, technology. Many different designs were built and tested for many applications varying from
short range target practice (they could bemade light and designed to choke at will) through antiaircraft (they were light, could be fired at high velocity, and out bigdeep holes) to armour piercing (high sectional density yields good penetration). Some work is still being done on tubular projectiles. Some of the past work is classified. So far as is known, none are in inventory. Like so many technological phenomena of academic interest, it is difficult to find a real application for it."

Pict.30:
Short version tubular projectile.

Pict.31:
Sabot test. An experimental NWM projectile, supposedly to test the lower aluminium sabot or test/measure ballistic data.

Pict.32:
Dutch powder test short range cartridge. Used to fire a test powder charge under normal barrel conditions. After leaving the barrel, the projectile becomes a short range projectile. Shellcase with EMZ base stamp.

Pict.33:
Blank cartridge. The body is made of black PVC. On the inside a white PVC container housing is placed housing the powder. The base is made of brass and has a stamped in text: 02-BF-00. BF is the abriviation for Bakelit Fabriken. Both the inner container as well as the plack plastic body have ripping grooves in top that rip open when under pressure when fired.

Pict.34:
Drill cartridge M86 B3. The lower part is made of a normal shellcase, the middle part is made of white nylon, the dummy fuze is made of aluminium. A threaded rod is screwed in the base of the shellcase. The dummy nose fuze is screwed over the threaded part of the rod, keeping the assembly together. The drill cartridge is most probably of US manufacture.

Pict.35:
Swiss Drill cartridge. This cartridge has a large flat head screw in the base of the shellcase. On the inside an aluminium intermediate piece is placed over which the dummy projectile is screwed.

Pict.36:
Dutch drill cartridge 25MM EXC BG NR232 (Exercitie Brisantgranaat Nr.232 / HE Drill cartridge Nr.232). On the inside the cartridge resembles the Drill cartridge of Pict.35. However, as to comply with Dutch rules according to drill cartridges, the shellcase has four holes drilled at 90 degrees each, and the whole cartridge is painted bronze colour. It is also marked with extra large stamped in text 25MM EXC BG NR232.


A big thank you to BLU-97 who helped me with adding a number of interesting 25x137 mm cutaway models to my collection, as well as being a great source of info.


Regards, DJH

Exceptionally fine work and information!!!!

Very nice DJ see you soon

The projectile is probably one of a series designed by Abe Flateau. The tube can be configured aerodynamically in two ways. The tube can provide flow through at a certain velocity but as the velocity drops it chokes and causes the projectile to slow and drop. This provides a short range round. On the other hand the tube can be used as a tubular aerofoil and as the velocity drops the tube alters its angle of attack and creates lift. This increases the range. The tube at terminal ballistics proved particularly damaging to aircraft airframes. Royal Ordnance used the former to create a short range A/T training round called (I think) STUP.

The May 2006 issue of the ECRA Bulletin has a long article about the Hebler tubular bullets (originally Krnka-Hebler), including a patent document dated 1893 (there is nothing new under the sun!). The same issue included a brief summary of the modern work by Abe Flateau.

Was there a tubular short-range training round for the 30mm Rarden or is my memory playing tricks on me again?

Correct Tony. The DSRR round. The patents are all online.

C.

Very old pick here 2007 ?!

http://www.bocn.co.uk/vbforum/threads/3483-30mm-Rarden-DSRR-L15A1?highlight=rarden+dsrr

.

DJH I hope you don't mind me adding to your excellent thread with some photos of some variations.
All INERT.
Dave.

MPT-SD aka PGU-32/u