81mm mortier M43A1 high explosive mortar shell, USA

[pzgr40]

Cutaway model of a 81mm mortier M43A1 high explosive shell, as used in the US 81mm M1 mortar.
The design of the shell is WW2, this round however was produced in 1953.

The M43A1 shell consists of a cast steel body, machined on the outside at the top to form a forward bearing surface and a gas check. The shell weighs 3,11 kg body is filled with 0,553 pounds of TNT or Composition B (40% TNT + 60% ammonium nitrate)

The tail has a screw in primer cap in the base with a cartridge filled with ballistite above it.
Four small bags with incremental charges are placed between the tailfins, secured with a clip. Depending upon the required range the mortar is fired with four charges for the maximum range (3000 mtrs) either without incremental charges for the shortest range (183 mtr). Vo of the projectile is 270 mtrs/sec. Incremental charges can be removed for in-between ranges.

The fuze used is the PD M52 (PD stands for Point Detonating) (Pict 03 & 04).
The fuze consists of a lower fuze housing (01) containing the safety mechanisms, the out of line placed detonator, and a booster charge screwed into the base. The upper fuze housing (02) contains the spring loaded firing pin (09).
Functioning of the fuze:
Prior to firing, the safety wire (wire, see pict.04) that fixates the set back pin (03) is removed. Upon firing, the set back (03) pin moves backward against it’s spring (04), thereby releasing the spring loaded safety pin (05) that fixates the slider (06) as well as the primer/detonator (07) placed in the slider in the safe -out of line- position. As long as the mortar shell is in the barrel, the safety pin (05) cannot fall out of the fuze housing as it is stopped by the inner wall of the barrel, as soon as the shell has left the barrel, the safety pin (05) falls away.
In safe position the primer/detonator (07) is out of line with the firing pin (09) and the Tetryl lead (08). When armed the the slider spring (10) has moved the slider with the primer/detonator in line with the firing pin (09) and Tetryl lead (08). Upon impact the firing pin moves downward into the primer detonator, initialing the Tetryl lead, the booster charge and the main charge in the mortar shell.

The difference between the fuze PD M52 , the PD M52B1 and the PD M52B2 is as follows:
- the PD M52 fuze housing is fully aluminum made,
- the PD M52B1 fuze housing is fully Bakelite made,
- the PD M52B2 fuze has a Bakelite lower fuze housing, and an aluminum upper fuze housing.

Regards, DJH

 

[Eggburt1969]

I did notice some problems, the first being Composition B is 40% TNT and 60% RDX. It does not contain ammonium nitrate.

The second is that there are other charge loadings for early-loaded (WW II-era) M43A1 mortar bombs (shells in earlier US terminology, commonly projectiles in current US data):

553-558 g (1.22-1.23 lb) of TNT; or
531 g (1.17 lb) total weight charge combination of 445 g (0.98 lb) of 50/50 Amatol plus an 86 g (0.19 lb) TNT topping; or
581 g (1.28 lb) of trimonite (see later text).

As such the fuzed projectile weights with an M52 fuze are:

3.14 kg (6.92 lb) with TNT
3.11 kg (6.86 lb) with 50/50 amatol plus TNT topping; and
3.18 kg (7.02 lb) with trimonite.

Post WWII data:

A filling of 585 g (1.29 lb) of Composition B; and
A total wight of 3.24 kg (7.15 lb) with Composition B and an M525 series (200 g/0.44 lb) series fuze.

As to trimonite, here’s some info I have.

Trimonite

Originator: France
Composition: 88/12 Picric Acid/Mononitronaralene
Loading Method: Cast
Color: Cream to Yellow
Rate of Detonation: 6,900 m/s (21,000 ft/s)
Density: 1.60 g/cm³
Detonating Temperature: +300°C.
Melting Temperature: +105°C.
Reacts with Metals: Forms dangerous salts with most metals.
Hygroscopic: Yes
Solvent: Acetone

[FONT=&amp]Performance and properties will vary with the version. Data here was for version Number 1 ([/FONT][FONT=&amp]№ [/FONT][FONT=&amp]1).[/FONT]

 

[apfsds]

Another EPIC sectioning job! WOW! Looks factory made! Just awesome

Jason

 

[pzgr40]

Lots of more stuff to follow Jason
I think I need a second life to cut all the stuff IU still want to cut. Momentarely I am bussy with a German naval 15cm for a posting

Regards, DJH