40 mm Bofors AA guns made in GB and US

[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.

the Uniforms

Especially various headgears are helpful when it comes down to identify the nationality of a gun (but not where made).

So now it starts. You should be able to identify:
1) Carriage type
2) Wheels type
3) Sights type
4) Environment type
5) Nationality group

And these facts together gives an idea of where and when.
(Right answer could be found by the AWM number).