SA18 L/21 (37 mm)

37 mm Puteaux SA18 as mounted in the French tanks

Description

The 37 mm SA18 L/21 cannon is a French tank cannon. Also known as Puteaux SA 18 (or 37 mm SA 18 L/21 Puteaux), it is is a gun that first saw use in the First World War, but also the Second World War.

Vehicles equipped with this weapon

• FCM.36
• H.35

General info

The Puteaux SA 18, or Semi-Automatique 1918 Puteaux, was primarily mounted in armoured vehicles and its main use was to suppress enemy machine gun nests, pillboxes, and also infantry. It was a simple and reliable weapon for its role, with a high rate of fire, low chance of jamming, and it required only a single person to use effectively. There was a sight mounted to the left of the weapon, which allowed consistent and accurate suppressive fire. Although its penetrative power wasn't something to brag about, it was just enough to penetrate most armoured cars of the time.

Adapted from the SA16 infantry support gun, it first appeared as the main armament of the revolutionary Renault FT series. Unfortunately, by the outbreak of World War II, its penetration had fallen well behind armour development. The guns used on French tanks of the time were usually scavenged from existing tanks from WW1, which led to a performance normally unfit for the tank battle. The original WW1 rounds offering only a velocity of less than 400 m/s were replaced by higher velocity rounds with a velocity of 600 m/s from 1935 onward. This allowed the French gun to catch up with modern guns somewhat, though it is still considered relatively weak. Weighing 110 kg with shielding, the barrel is 21 calibres long. Having a rate of fire of 20 rounds per minute, the gun has a pretty good reload speed but the maximum effectiveness of his penetration is about 400 m.

Available ammunition

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
		10 m	100 m	500 m	1,000 m	1,500 m	2,000 m
Mle1937	APCR	36	33	24	16	8	5

Shell details
Ammunition	Type of warhead	Velocity (m/s)	Projectile mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	Ricochet
							0%	50%	100%
Mle1937	APCR	600	0.5	N/A	N/A	N/A	66°	70°	72°

Comparison with analogues

Comparable cannons to the SA 18 L/21
Nation	Name	Year of Production	RPM	Ammunition	Maximum Penetration
GER	PaK L/45 (37 mm)	1934	15 RPM	PzGr	47 mm

Usage in battles

The SA18 L/21 is, unfortunately, a gun in the wrong world war. Originally intended as a short-range support gun for easy transportation, it was designed as a basic, short-barrelled gun. While this meant it excelled in the role that it was intended for on the battlefields of the First World War, it also meant it quickly became obsolete in view of tank development on the eve of the Second World War. When used in combat against early World War II armour, it is only effective at very short range. If confronted with anything further than 100 m with more than 30 mm of armour, hold fire if you don't want to attract the enemy's attention.

Pros and cons

Pros:

• Very high firing rate
• Relatively accurate gun

Cons:

• Lack of penetration power (and that is an understatement)
• Light APCR round, doesn't do much damage upon penetration
• Low muzzle velocity, shell drops off very quickly, severely limiting its effective range

History

The 37 mm Puteaux SA18 cannon started life as a development of the Canon de 37 mm à tir rapide Modèle 1916 (SA16), a small but powerful, portable infantry support gun designed by Eugène François Gilbert Garnier (1874-1964) on the instigation of the generals Jean Estienne and Ferdinand Foch. The original purpose of the SA16 was a light gun capable of demolishing pillboxes and gunner nests, with a high rate of fire. Due to its intended use, its range was not considered a priority as part of the gun's design: the result was a relatively small and light weapon, with very high accuracy. When operated by an experienced crew, the gun could fire up to 15 shots per minute, although it had a practical firing rate of 10 shots per minute under normal circumstances. Despite its relatively small size, the original infantry gun would be operated by a crew of 8, consisting of commander, aimer, gunner, four ammunition handlers and one armourer.

With the advent of the first tanks, a variant of the SA16 was developed which could be operated by a single crew member. This gun, the SA18, was technically similar to the SA16 and capable of firing the same ammunition. Crucially though, the gun was never intended as an anti-tank weapon: its primary goal remained that of infantry support gun tasked with destroying enemy machine gun emplacements, the only thing conceptually changing was the addition of a self-propelling function (i.e. the Renault FT-17 tank built around it, allowing it to autonomously move on the battlefield rather than being fired from a static position).

The end of the First World War more or less brought tank development to a halt in Europe. In the absence of any concrete threat and with French tank doctrine firmly based on experience during the First World War, the SA18 was seen as sufficient for the task of providing supporting fire for infantry against enemy troops and fixed gun emplacements. Added to this, the reconstruction of France after the destruction of the First World War and the worldwide economic crisis which erupted at the end of the 1920s, combined with a general anti-war sentiment reigning in politics meant there were little in the way of funds available for the development and replacement of the SA18. Even with a new generation of tanks which were developed at the beginning of the 1930s, these were armed by simply removing the SA18s from the Renault FTs they were supposed to replace and then installing them on the new tanks. As a result, this new generation of tanks, the Hotchkiss H.35, Forges & Chantiers de la Méditerrannée FCM.36 and the Renault R.35 entered production with the outdated gun, even though attempts were made to improve its capabilities by the development of new types of shells. The Obus de rupture Modèle 1935 APCR round offered a higher muzzle velocity than previous ammunition used on the gun, but as it was relatively light it could only do little damage even when if it by chance happened to penetrate.

By this time, the SA18 was seen as an interim solution: the FCM.36, for instance, had been designed with the SA38 in mind, and it received the SA18 with the intention of having it replaced at later date with the SA38. However, owing to a weak turret ring and other structural problems, this refit never came to be, and the FCM.36 entered battle in May of 1940 with a gun that was virtually incapable of penetrating any of the enemy armour it would oppose.

Despite being completely obsolete by the outbreak of World War II, the SA18 and its infantry counterpart, the SA16, were still widely in service and saw combat with several armies, such as France, Belgium, Poland, Yugoslavia and Finland.

Historical rounds details

While in-game only a limited number of types of ammunition was made available for this armament, the SA18 had a pretty wide range of ammunition available. Sadly most of them are simply too weak to be used in an anti-tank role.

Performance values are estimations based on the information available and might not be 100% accurate

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
		10 m	100 m	500 m	1,000 m	1,500 m	2,000 m
Mle 1888	APHE	12	10	6	4	2	1
Mle 1916	AP	16	14	9	7	5	2
Mle 1892 m.24	APHE	16	14	8	6	4	2
Mle 1935	APCR	27	24	15	10	8	6
Mle 1937	APCR	36	28	18	12	9	8
Brandt 37/25	APDS	54	51	45	38	30	23
Mle 1916	HE	2	2	2	2	2	2
Mle 1937	HE	3	3	3	3	3	3

Shell details
Ammunition	Type of warhead	Velocity (m/s)	Projectile mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	Ricochet
							0%	50%	100%
Mle 1888	APHE	401	0.455	0.5	0.1	22	47°	60°	66°
Mle 1916	AP	410	0.45	N/A	N/A	N/A	47°	60°	65°
Mle 1892 m.24	APHE	388	0.555	0.5	0.1	15	47°	60°	65°
Mle 1935	APCR	600	0.39	N/A	N/A	N/A	66°	70°	72°
Mle 1937	APCR	600	0.5	N/A	N/A	N/A	66°	70°	72°
Brandt 37/25	APDS	825	0.30	N/A	N/A	N/A	75°	78°	80°
Mle 1916	HE	440	0.367	0.01	0.1	30	79°	80°	81°
Mle 1937	HE	440	0.555	0.01	0.1	56	79°	80°	81°

Obus en fonte Mle 1888 (APHE)

A training round with a blunt tip.

• Weight: 455 g
• Velocity: 401 m/s
• Explosive filler: 22 g

Obus de rupture Mle 1892 m.24 (APHE)

The most used round for the SA18. Initially designed for usage in WW1, this round was meant to provide some support against rather hard targets such as houses, pillboxes and trenches, but not really made for armoured vehicles as it was designed in a time where there was no armoured vehicles. It was made of steel with a bit of explosive filler made of black powder.

• Weight: 555 g
• Velocity: 388 m/s
• Explosive filler: 15 g

Obus ogival plein Mle 1916

Initially used for instruction, it was used in WW2 for anti-tank purposes. This round was a simple round made of steel. It could not really be effective against a proper tank, but it would be capable to destroying armoured cars.

• Weight: 450 g
• Velocity: 401 m/s

Obus de rupture Mle 1935 (APCR)

Improved rounds designed for anti-tank use. It was a solid round made of magnesium and hardened steel (possibly having 3% tungsten). This round produced a white flash on impact with possible incendiary effects.

• Weight: 390 g
• Velocity: 600 m/s

Obus de rupture Mle 1937 (APCR)

More compact rounds based on the Mle 1935 with a magnesium cloak and hardened steel core. This round also produced a white flash on impact with possible incendiary effect.

• Weight: 500 g
• Velocity: 600 m/s

Brandt 37/25 APDS, this round was considered experimental but rushed during the last weeks of the battles of France. 200,000 were ordered, but it is unknown how many were produced before the end.

Obus Brandt 37/25 (experimental APDS)

Experimental sub-calibre round tested in late 1939/1940 to improve the 37 mm gun, this round was said to be capable of providing performance similar to the 25 mm SA34 anti-tank gun. It was made with a 25 mm projectile with a possible 20 mm tungsten core. There seems to have been an order of 200,000 of these rounds for the army but there is no details about whether this order was delivered or not.

There is not much detail about this rounds weight, the weight is estimated to have been between 295 and 310 g.

• Weight: 305 g
• Velocity: 825 m/s

Obus explosif Mle 1916 (HE)

Standard WW1 high-explosive round used for support and clearing trenches.

• Weight: 367 g
• Velocity: 440 m/s
• Explosive filler: 30 g

Obus explosif Mle 1937 (HE)

Improved explosive round carrying more explosive than the previous one making it a rather good support round.

• Weight: 555 g
• Velocity: 440 m/s
• Explosive filler: 56 g

Media

Excellent additions to the article would be video guides, screenshots from the game, and photos.

See also

Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:

• reference to the article about the variant of the cannon/machine gun;
• references to approximate analogues by other nations and research trees.

External links

• [Wikipedia] Puteaux SA 18
• French manual of 37 mm rounds
• French manual of the 37 mm TR 16 from WW2
• Conversation of the investigation on the battle of France (chief engineer talks about experimental rounds)
• France 1940, L'armement terreste, by Stéphane Ferrard, page 93-94