How to Indentify the WW2 or Mk.I, Mk.I or Mk.III Bofors 40mm ?

[Kurtis Tsang]

Hi,

I am not sure if anyone had discuss this topice before. I found some discrepancies for the different Canadian Bofors in different museums.

The discrepancies are mainly for the platform, travellock, towing hook.
I am not sure if the "single platfrom" at the left side is post war version. Or all of them are WW2 versions, the different details are based on Mark I, II or III ??

Does anyone can help to indentify ? Thanks in advance.

Here are some example, single platform Bofors could be found from Primeportal website:

http://data.primeportal.net/artiller...m_01_of_13.jpg

http://data3.primeportal.net/artille...s_64_of_90.jpg

Brad's example is one piece platform and the towing hood is different.
http://www.mapleleafup.org/forums/showthread.php?t=9331

Kurtis

[Stellan Bojerud (RIP)]

How to identify a 40 mm Bofors L/60 gun.

The Gun

It is only possible to see if a gun is of the air-cooled type or the water-cooled Navy type.

There are however three types of Army Bofors guns:

1) Made in Europe (except Great Britain)
2) Made in Great Britain and Commonwealth
3) Made in USA

Type 1 guns are handicraft made. Types 2 and 3 mass-production. In USA Chrysler managed to reduce production hours for making a gun with some 50%.

The only way to identify the gun itself is by finding the marks on various parts. Mainly on the left side of the breech.

The carriage

The carriages are of five main types

1) Rivetted short wheelbase. Jacks outside the wheels. Wheels still attached to carriage also when the gun is in battery position. Box shaped outriggers.

This type is found on:

a) Various European countries guns
b) British Mk I and Mk IA
c) US M 1 (British made - some 200 to USA from GB early 1942)

2) As above but welded. Only US carriage M 2 wich was standard during WW 2.

3) Welded long wheelbase. Jacks inside the wheels. Wheels removed when in battery position. GB carriage Mk II and Canadian Mk C 2. Round shaped outriggers.

The GB Mk III carriage is similar to Mk II but have only overrun brakes on front wheels.

4) Two wheel carriages for air transport. GB and US variants.

5) Self Propelled mounts on trucks and tanks.

Armoured protective shields were added to British carriages (both MK I and MK II) in 1944. US Army guns did not have shields during WW 2.

Of the Axis powers only Hungary added shields in 1944.

The Wheels

The wheels could by dimension and type of wheeldisc be divided in:

1) European type
2) British and Commonwealth type
3) US type

The Sights

There are several types of sights and those could help to identify nationality and time period.

1) Optical reflex mirror sights. By the British called "Polish" sights. These were attached to a predictor or target calculator attached to the right side of the breech.

The calculators were of three main types. Bofors, Goerz and Johasz-Gamma but the sights for these types looks basically the same.

2) Early pre-1943 GB "small spider-web" sights. The left sight (elevation)with cross-wires and the right (traverse) with three vertical wires. Called "Forward Area Sighting System".

3) GB 1943 "large spider-web" sights. Three crosswire rings for target speed 100 - 200 - 300 mph. Called "Cartwheel Foresight" or sometimes "Pancake sights". On the Australian version the right (traverse) sight is almoast rectangular.

4) The US standard "spider-web" sights are somewhat larger than the early GB type but smaller than the GB 1943 type.

5) GB 1944 Correctional Sight called "Stiffkey-Stick". This has a calculator attached above and somewhat right of the left (elevation) sight. This sight require a special sight operator in addition to the two gunlayers. The sight operator was standing on the platform between and behind the gunlayers.

6) US 1944 "Sight Computing" M 7 and M 7A1 is a US made "Stiffley-Stick" and operates in the same way.

7) The GB No 3 Predictor or "Kerrison-Predictor" is a box with two small binoculars. It was placed on a tripod (or post 1943 on a separate truck) and attached to the gun with an electrical cable. On the gun platform there were two electrical motors for laying the gun.

[Tony Smith]

Originally Posted by Kurtis Tsang

The discrepancies are mainly for the platform, travellock, towing hook.

On the Commonwealth made versions (Mk2?), I have seen two types of drawbar, an enclosed box section, and a 2 parallel rail type. Any ID on either type?

[Tony Smith]

Originally Posted by Kurtis Tsang

The discrepancies are mainly for the platform, travellock, towing hook.

By Travellock, do you mean Barrel Clamp? On the Commonwealth made versions (Mk2?), I have seen 3 different versions. The most common type seems to be the "Wide frame" bracket, there is also a "Narrow frame" and another variation, very similar to the screw clamps of the MK1:

[maple_leaf_eh]

I've got a 1943 Popular Science magazine that has a story on welding, and how progressive welding is winning the war! Plenty of war production stories, including one on how to weld. There are pictures of some AA gun carriage that was improved over riveted construction. More to follow.

[Kurtis Tsang]

Hi Tony,

Thank you very much for the info. It is exactly what I want to know. Thanks.

Kurtis

[maple_leaf_eh]

Originally Posted by maple_leaf_eh

I've got a 1943 Popular Science magazine that has a story on welding, and how progressive welding is winning the war! Plenty of war production stories, including one on how to weld. There are pictures of some AA gun carriage that was improved over riveted construction. More to follow.

April 1943 Popular Science (Vol 142 No 4) .25 cents, (cover story, 'Shall we quit building battleships?' complete with a hard steaming battlewagon firing a broadshide from a storm-tossed sea and jaunty a Navy floatplane banking overhead) p. 82 'War Drafts the Man in the Mask' by Russell C. Holslag. On pp. 86 and 87 are photos with captions describing the carriage for the 40mm Bofors and how this is the progressive use of modern welding and fabrication techniques in the rest of the article. In an American use of the English language, there are no periods after the last word in the captions.

From the captions it seems that a Bofors gun was reverse engineered, or with drawings for product improvement.

Caption top page 86, "At left, the elevating arc sector of the gun in its original riveted form and as it is now being welded. At far left, the same comparison is shown in part of one of the gun's outriggers" Forty-one rivets counted as received, vs zero in new production.

Caption botton page 86, "A good example of the vital role welding has played in war production is found in the American manufacture of the Swedish Bofors 40-mm automatic antiaircraft gun. Originally its gun carriage was riveted throughtout. By the substitution of welding, enormous savings in time, manufacturing costs, and materials have been effected. At above left is shown the welded front, or swivel, end of the gun chassis as compared with the riveted end, below"

Caption top page 87, "Because of its unusual effectiveness in defending troops against low-flying enemy planes, the Bofors gun has now been widely adopted by both British and Americans"

Caption mid right page 87, "Above, the carriage as it appeared when first imported into the U.S. to serve as a model for American builders, and at left, the carriage as it now appears, welded"

On page 87 is a small font credit, "Data and illustrations from study submitted to James F. Lincoln Arc Welding Foundation by Dr. John L. Miller of the Firestone Tire and Rubber Co."