Bofors 37mm Anti-Tank Gun for Phoenix Command

The Finnish Weapons Series

Bofors 37mm Anti-Tank Gun

A Finnish-manufactured Bofors AT gun. The hinged lower gunshield has been partly folded up for easier transportation over broken terrain.

This is my third version of the Bofors anti-tank gun. If you have additions or comments please let me know.

Bibliography:

-:Jalkaväkitykkijoukkueen koulutusopas - 37 mm:n panssarintorjuntakanuuna. Jalkaväentarkastajan toimiston julkaisu. Puolustusministeriö, Koulutusosasto. Kustannusosakeyhtiö Otava, Helsinki 1939.

The Finnish Armour Museum permanent exhibit, Hämeenlinna.

Halsti, Wolf H: Talvisodan päiväkirja. Otava, Helsinki 1971.

Huhtala, P.: Reserviupseeri - Reserviupseerien ja -aliupseerien kertaus- ja jatko-opiskelukirja. Werner Söderström Osakeyhtiö. Porvoo 1940.

Hämäläinen, Valde: Rivimiehenä talvisodan Summassa. Akateeminen kustannusliike. Helsinki 1976.

Käkelä, Erkki: Marskin panssarintuhoojat - Suomen panssarintorjunnan kehitys ja panssariyhtymän panssarintorjuntayksiköiden historia. Werner Söderström Osakeyhtiö, Helsinki 2000.

The Military Museum Winter War exhibit, Helsinki 1999-2000.

Partanen, Unto: The 78 Guns of the Finnish Artillery Museum. Tykkimiehet ry, Tykistömuseo. Hämeenlinna 1988.

Salt, John: World War 2 Snippets web site previously at http://www.brunel.ac.uk/~csstjds/WW2stuff.html

All photos published with the kind permission of the Finnish Armour Museum.

Data:

Bofors 37mm Anti-Tank Gun


 Barrel length:          45 cal             
 Weight unloaded:        816 lb  (370  kg)

 Thickness of gunshield: 4-5 mm
    Angles:
      Protecting crewman's head     : 50 degrees
                           chest    : 15 
                           abdomen  : 40 
                           upper leg: 90 
                           lower leg: 78 

 Muzzle velocity:        2625-2723 fps (800-830 mps)
 Range:                  4376 yd  (4000 m)
 Elevation:              -10  +25 degrees
 Traverse:                25 degrees 

 Penetration:    Range, m     mm at 60 degrees
                  300         40   
                  457         33      
                  600         30   
                  900         20   
                 1000         20      
                 1200         15   


 Ammunition: AP with tracer, HE fragmentation and WP incendiary 
  AP tracer round m/34
    Weight, entire round:  1.45  kg, 2.0 kg in package
    Weight, projectile:    0.70  kg
    Maximum range:         6500  meters


 Rate of Fire: 
    "12 well-aimed shots per minute while engaging a moving target"
    Semi-automatic breech.

Stats:

Bofors 37mm Anti-Tank Gun
   37 PstK 36 
   37 mm pakanon m 34
   Armata przeciwpancerna wz36 
   Ordnance Q.F. 37 mm Mk 1
   3.7 cm Pak 36(p)

 
 Nationality: Sweden with license manufacture in other countries
 Initial Service: 1935 ?

 Weight: 838 lb  (380  kg)
 Crew: 11 or 12
 Gunshield PF: 
      Protecting crewman's head     : 16.1
                           chest    : 44
                           abdomen  : 23 
                           upper leg:  6.7 
                           lower leg:  7.6 


 Elevation:     -10 / +25 degrees
 Traverse:       25 degrees
 Traverse rate:  71 degrees / Phase

 Deploy   Time:     4 Turns (16 Phases)
 Break    Time:     2 Turns ( 8 Phases)
 Rotation Time:    39 degrees / Turn, (10 degrees / Phase)
 Set      Time:     1 Turns ( 4 Phases)

 Manual Movement Speed 2.5

 Weapon Characteristics
  RT     2P, 8 CA

  Target Size
    Front            12   
    Front Dug In      9
    Side             13
    Side Dug In      10

 Critical Hit Chance
    Front            70
    Front Dug In     76
    Side             67
    Side Dug In      75


 Aim Time: Ph CA  Md  
           1   4 -12
           2   8  -7
           3  12  -4
           4  16  -3
           5  20  -1
           6  24   0


 Direct Fire Data, 20 Yard Mech Hexes and 2-meter hexes:

 MH        4  10  15  20  30  40  50  60  70  80  90 100 120 140 160
 mhex     37  91 137 183 274 366 457 548 640 731 823 914 
 -------------------------------------------------------------------
 AP  PEN 259 211 176 115 110 102  90  50  41  34  28  23  15  11 7.5 
     AOI           -   -   -   -   -   -                           1
     NID   2   2   2   2   1   1   1   1   1   1   1   1   1   
     DFE 209  79  51  36  22  15  11   9   7   5   4   4   3   2   1
     BA   35  26  22  19  15  11   9   6   4   3   1   0  -2  -4  -6
     TOF   1   3   4   6   8  12  16  21  24  25  26  27  29  31  33
     BC0   0
     MCD   1

 MH        4  10  15  20  30  40  50  60  70  80  90 100 120 140 160
 mhex     37  91 137 183 274 366 457 548 640 731 823 914 
 -------------------------------------------------------------------
 HE  PEN  62  58  55  52  47  42  37  33  30  27  24  22  18  14  12
     PENF 38  35  33  31  28  25  22  19  17  15  14  12   9   7   6
     AOI                                                           1
     DFE 209  79  51  36  22  15  11   9   7   5   4   4   3   2   1
     BA   35  26  22  19  15  11   9   6   4   3   1   0  -2  -4  -6
     TOF   1   3   4   6   8  12  16  21  24  25  26  27  29  31  33
     BC0 431
     DFS  



   HE shell concussion and fragmentation data:
      C   0    1    2   3    4   5    6   8   10  12  15  20  30  40
 PEN 2.5 1.2  1.2  1.2 1.1  1.1
  DC 10   2    2    2   2    2
BSHC *3   3    0   -5  -8   -10
  BC 64h 424  115  35  18   11   8    6   3    2   2   1   1   1   1

We saw this huge ugly thing coming with its tracks rattling madly, right towards our gun intending to ram it. Our gun was immediately adjacent to our bunker and there was now but a few score meters between us and the tank. Behind this first one came the 'little ones', the smaller tanks. It was continuously firing with its machine guns but because it wobbled and bucked as it rolled on forward we did not pay much attention to that. Far more worrysome was the short-barreled, large-bore cannon which was slowly rotating towards us.

They're so close ! They'll squash us under them I thought. Vasama threw himself down onto the limber and tore open the breech. Murtojärvi slammed the shell in there. Only with difficulty did I dare to take my usual place standing, directing fire.

A shot. It went off the very moment the breech closed with a clink. A miss !

Missed towards the left. Correct slightly towards the right, I cried.

The column of tanks continued to rattle on towards us. The distance was now less than twenty meters. If the next one did not hit we would be done for.

Fire ! I screamed.

The first tank, the giant one, now had its cannon trained on us. The gaping maw was ready to spit fire and steel. Who would go first ? We now had the benefit of a ranging shot.

Another shot went off. It was our gun. There was no time to ponder whether it had been by a second or a fraction of a second that we were quicker than the gunner encased in armor.

A hit... a hit in the turret !

The Bofors was a fine gun. The turret's armor could not withstand it and gave away. Later that evening we found out that after penetrating the turret the shell had gone right through the gunner, standing by his cannon, and flung his body backwards so that it became stuck between his seat and the turret rear wall. The body could not be extracted from there.

2nd lieutenant V. Hämäläinen's account of
a duel between his crew and a fifty-ton
T-35 tank on February 11, 1940

Specialized anti-tank guns came into widespread use in the Thirties, the first examples being typically of 20 or 37mm caliber. 37mm guns were produced by the USA (M3), Germany (Pak 36), Japan (Model 94) and various other countries. The Swedish Bofors design was very successful and won a number of license manufacturing contacts around Europe. It was produced by Poland and Finland at least and was used by these countries' armies as well as by Britain and Denmark. After the invasion of Poland the Germans adopted the model as the 3.7cm Pak 36(p).

In 1939 the Finnish government decided to obtain 156 Bofors cannon. However only fifty had been manufactured by the time the Winter War broke out. Thus the country had only one AT gun for every forty invading Soviet tanks. The rest of the guns were produced during the war and an additional eighteen were bought and thirty more borrowed from Sweden. In late April 1940 fewer than 70 guns remained. About 150 further guns were produced in Finland after the Winter War and twenty Polish-made war booty guns were bought from Germany in 1941.

The Bofors gun featured a muzzle-brake and a semi-automatic breech. In the Winter War it seems the guns were often issued with armor-piercing ammunition only though HE shells were also available. In 1936, the high-velocity AP round was more than able to pierce all existing tanks. The barrel's rifling gave it a spin toward the right - at a range of 500 meters the effect of this was 50 centimeters, at 900 meters 150 cm towards the right. The main sight was an optical device but backup iron sights were also fitted.

A Swedish-manufactured piece. Note how the edges of the gunshield are irregular and do not form the square shape which tankers will be looking for.

The gunshield, which protected the crew against shrapnel and rifle caliber rounds, was hinged so that its lower part could be turned up during transport which made it easier to move the gun over broken terrain. The shield of Swedish-made guns had an irregular shape which made the weapon more difficult to spot.

A Finnish anti-tank gun platoon of 1939 had the following order of battle:


AT-gun platoon
   Platoon leader
   Command Squad
   Two or more AT-gun squads, each with 
      NCO Gun Commander with pistol, rifle, binoculars, compass, map case, 
          whistle, flashlight and bicycle 
      Gunner with rifle and axe
      Loader with rifle and entrenching tool
      Loader's Assistant with rifle, entrenching tool and tow line
      Reserve Man with rifle, pick and tow line
      Observer with rifle, wire cutters, binoculars and compass
      Ammunition Man with rifle and axe
      Ammunition Man with rifle and entrenching tool
      Ammunition Man with rifle and axe

      In a horse-drawn unit:
        3 Teamsters with rifle
           (often with an additional Teamster per squad or platoon for taking 
            care of spare horses)
        Three horses and one spare horse
        Bofors gun and limber with two-cheeled cart
        Two carts or sleighs for transporting ammunition and equipment 
           (including a shovel, axe, pick and saw) 

      In a motorized unit: 
        Two drivers with rifles
        Gun-towing truck 
        Ammunition truck for transporting ammunition and equipment
           (including a shovel, axe, pick and saw)
        Bofors gun and limber with two-cheeled cart

The gun's ammunition and equipment was typically transported on a small, two-wheeled cart drawn by one horse. The gun was limbered onto this cart.

In combat the Gun Commander stood on the left side of the gun, directing fire. He observed the field of fire, selected targets and called corrections. The Gunner lay on the left limber, his right hand on the elevation lever and his left on the horizontal adjustment wheel. The Loader lay on the right hand side limber and loaded rounds passed to him by his Assistant. The Assistant's position was at knee half a meter from the Loader and his job was to open ammunition cases and to wipe the rounds clean before passing them to the Loader.

The padding on the limbers are what passes for the gunner's and loader's seats.
The gun's sight has been removed but would be on the bracket next to the square hole in the gunshield.

The Reserve Man was to lie prone behind the Assistant ready to take over from any of the crew if they were incapaciated. He could also help the Assistant or the Ammunition Bearers, who were to place the ammunition crates next to the Assistant and to bring him more crates as needed. The Observer helped the Gun Commander with any observing duties he would assign him.

The standard procedure for moving the gun in combat was to have the Gunner, Loader, Loader's Assistant and the Reserve Man push or pull the weapon, keeping the barrel pointed towards the enemy. Usually the gun was placed in a specially dug depression where it was under cover and it was brought into a prepared firing position only moments before fire was opened.

The tank opens up with its cannon. We see that it has stopped at the enemy's front line and is now shooting along the road. Our gun remains hidden. Then the tank's cannon turns towards the side. Our gun is raised into firing position, the crew working frantically. The gunner is behind his sight, turning the wheels. A sharp bang. A long flame shoots out of the barrel and we hear a clear ringing sound from the direction of the tank - a hit !

Captain Wolf Halsti's account of night combat between
a Bofors AT gun and a T-26 tank on February 17, 1940.

When necessary, the gun could be pulled away under enemy fire - staying low behind the cover provided by the gun shield, the men would crawl and pull the gun after them using tow lines.

A Polish-manufactured Bofors. The horizontal adjustment wheel (on the left) and the elevation wheel with what is probably the trigger are clearly visible. The upright paddle is there to prevent the gunner from accidentally placing himself behind the gun's breech. When the gun is fired the barrel and breech assembly will recoil back, causing considerable injury to anyone in the way.

With its good performance, high rate of fire and motivated crews, the 37mm Bofors was extremely successful against primitive Soviet armor such as the T-26, BT, T-28 and even the monster T-35. The low shilouette and white-painted gun shield along with the inadequate vision systems of early tanks made it difficult for the tankers to see the Bofors even when it was firing. But with the introduction of the KV-1 and the T-34 during the Continuation War, the small-caliber gun was quickly relegated to infantry support functions but was not removed from Army inventory listings until 1986.

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