M- 40 A1 Recoilless anti-tank rifle

Recoilless rifles were developed during WW2 by the Germans as lightweight anti-tank weapons. The 75mm Panzerabwehrwerfer was a 75mm weapon developed for airborne use and it was followed by a 105mm version based on the same principles. The recoilless action was achieved by venting gas through the rear of the gun and this technology was pretty much directly copied by the Americans who had also brought recoilless weapons into service by the end of the war. The initial American M-18 57mm &  M-20 75mm weapons were joined in the early 1950s by the M-27 105mm gun with these being regarded as the most effective anti-tank technology of the time. The M-27 105mm gun turned out to be both inaccurate and unreliable and therefore had to be redesigned. Its replacement, the M-40, was also a 105 calibre weapon but to distinguish it from its predecessor it was designated as being a 106mm weapon even though it wasn't! This designation did mean. however, that ammunition for the two guns did not get confused.

Norwegian army trailer mounted M-40 A1

The principles of the M-40 recoilless rifle are fairly simple. The shell has a rifled driving band that engages with the rifled barrel of the gun. This causes the shell to spin on firing creating stability in flight. The shell case is perforated so that whilst some of the gas pressure forces the shell forwards an equal amount of pressure escapes through the perforations and exits through the rear of the breach, hence no recoil. The fact that not all of the charge is used to propel the shell forwards means that a larger than normal charge has to be used and both the velocity and range of the weapon is rather less than that of a similar calibre conventional gun.

Rifled barrel of an M-40 A1  

The 75mm weapon (M20) was an ideal size to be mounted on a jeep but it lacked range and penetrating power so it was replaced by the larger and redesigned M-40 106mm recoilless rifle but this required rather more modification of the jeep. To facilitate this an adjustable M-79 wheelbarrow mount was produced that would fit into most models of jeep that were in service at the time and which could be demounted for field use if required. During the 1950s the French army obtained the 75mm M-20 from the US to deploy on its jeeps but 6 volt M201 mounted 106mm M40 guns were introduced as a replacement probably by 1957 (M201 106SR No. 2924 was auctioned off as an un-rebuilt jeep). 

Demounted M40 being used to fire HEAT rounds.   1964 M201 106SR  with 4 rack mounted rounds in protective tubes.

The M-40 rifle was fitted with an M-8C 50 calibre semi-automatic spotting gun mounted on top of the main barrel which fired shorter than standard 50 calibre phosphorus tipped spotting tracer rounds designed to have the same trajectory as the main 106mm round. These produced a bright red trace followed by a yellow flash and smoke on impact. The weapon was aimed using an optical sight then the spotting gun used to check this before the main round was fired using the same trigger lever.  The photos below are of a 1958 M201 taken from French army training manual MAT6050. Note the up rated cross ply tyres fitted to these at the time.


Batches of new M201s continued to be converted by ERGM at la Maltournée certainly up to 1964 and both obsolete missile launchers and worn out 6 volt 106SRs were being rebuilt as 24 volt106SRs as late as 1974. In 1975 ERGM started converting M201s to carry the anti-tank MILAN missile system. As far as I can tell from my database no further 106SRs were produced, indeed some of the older 106SRs were converted to being MILAN launchers. It is difficult to give a date when the French army withdrew the weapon as it was more a case of phasing it out. Judging by the Sword & Tricolour markings my 106SR remained active into the 1990s and was finally sold off in 1999 but I suspect that it was one of the very last few to be in active service up to that time. 

One significant disadvantage of the recoilless rifle can be see in the photo by Tom Taylor opposite which shows the gun being fired from an M-151 Mutt jeep. There is a very large amount of smoke created behind the gun where a cone shaped  exclusion zone about 70m deep and 130m wide has to be enforced. On firing, the vehicle's position is almost certainly given away making it imperative that the shot was on target!

The M40-A1 / A2  is no longer in use with NATO countries but its cost-effectiveness has meant that it is still manufactured in India and remains popular with the less well off armies of the world. I have not managed to find the current price of a new gun but HEAT shells will set you back about $750 each and they still come packed in the same tubes, two at a time in wooden crates. Before you get too excited, an export licence is needed to purchase!

If you miss - run away quickly!

Finally, a quick explanation of the four types of round for the M-40 A1. Apart from inert drill rounds which were weighted to simulate handling the real thing, there were three types of live round:

HEAT - High Explosive Anti- Tank. The explosive charge is focussed on a small spot of armour, punching a hole in it and leaving a surrounding scorch mark.

HEP-T - High Explosive Plastic with Tracer - On impact the explosive is flattened against the armour before being detonated. This creates a shockwave that breaks off a chunk of armour on the inside sending fragments everywhere at high velocity. Only a scorch mark is evident on the outside.

The other type of round, APERS  was a fragmentation shell for anti personnel use.