Smith Gun The Smith Gun was an " ad hoc " anti - tank artillery piece used by the British Army and Home Guard during the Second World War . With a German invasion of Great Britain seeming likely after the defeat in the Battle of France , most available weaponry was diverted to the regular British Army , leaving the Home Guard short on supplies , particularly anti - tank weaponry . The Smith Gun was designed by a retired Army Major named William H . Smith as a makeshift anti tank weapon , and was put into production in 1941 following a demonstration to the Prime Minister , Winston Churchill . The weapon consisted of a 3 - inch smoothbore barrel approximately 54 inches long mounted on a carriage and capable of firing both anti - tank and anti - personnel rounds to ranges of approximately 500 yards . Despite the promising - sounding nature of the weapon it had several problems ; the effective range was only around 100 – 300 yards , it was a heavy and awkward weapon to move around and it developed " a terrifying reputation for killing its crew . " Production problems meant that it was not introduced until 1942 , when it was issued mainly to Home Guard units and those units in the regular Army tasked with guarding airfields , and ammunition shortages meant that the guns had only six or seven rounds each . Despite these problems many Home Guard units developed an attachment to the weapon , later claiming it was " one of the best pieces of equipment ever issued to the force . " Development . With the end of the Battle of France and the evacuation of the British Expeditionary Force from the port of Dunkirk between 26 May and 4 June 1940 , a German invasion of Great Britain seemed likely . However , the British Army was not well - equipped to defend the country in such an event ; in the weeks after the Dunkirk evacuation it could only field twenty - seven divisions . The Army was particularly short of anti - tank guns , 840 of which had been left behind in France and only 167 were available in Britain ; ammunition was so scarce for the remaining guns that regulations forbade even a single round being used for training purposes . Given these shortcomings , those modern weapons that were available were allocated to the British Army , and the Home Guard was forced to supplement the meagre amount of outdated anti tank weapons and ammunition they had with " ad hoc " weapons . One of these was the Smith Gun , which had what Mackenzie describes as an " unorthodox " origin , like many of the other weapons that were produced for use by the Home Guard during the conflict . It was invented by retired British Army Major William H . Smith , the director of a civil engineering company that produced toys , and was intended to be a cheap and easily - manufactured anti - tank weapon . The weapon design was submitted to the Ordnance Board , who were not convinced of its merits , but the Prime Minister , Winston Churchill , witnessed a demonstration of the weapon in 1941 and ordered that it be put into production . Design . The Smith Gun consisted of a 3 inch calibre smoothbore barrel 54 inches in length , which was mounted on a carriage which looked " like a two - wheeled baby carriage " and weighed approximately 604 pounds . A shield was erected between the two wheels to provide cover for the crew . The weapon had an unusual firing procedure , in which it was actually tipped over onto one wheel , this acting a baseplate and thereby allowing the Smith Gun to be rotated 360 degrees with a 40 degree elevation . It was light enough that it could be towed behind a civilian vehicle , although it was not designed for this and Home Guard units had to be prohibited from doing so as it would damage the wheels of the weapon ' s carriage . The Smith Gun was able to fire both anti - personnel and anti - tank rounds , with the latter capable of penetrating some 60mm of armour at that range . Fletcher claims that it had a range of approximately 500 yards , although Mackenzie states that it had an effective range of only between 100 – 300 yards , and was also inaccurate . The weapon was found to have several flaws in its design , and as such was not well liked by some of the Home Guard units to which it was issued . It was heavy and awkward to manhandle , particularly over rough ground and in urban areas ; in the latter , it was recommended that toggle rope s be used to manoeuvre the weapon into position . It also possessed a low muzzle velocity ; and due to the initial supply of rounds possessing faulty fuze s it gained " a terrifying reputation for killing its crew . " Operational history . Production on the Smith Guns began in late 1941 , but problems with their manufacture meant that it was not until mid - 1942 that the first batch of 4 , 000 were delivered to the Home Guard ; by the beginning of 1943 , a total of 3 , 049 Smith Guns had been issued to Home Guard units . Production problems also affected the ammunition for the weapons ; a delay in manufacturing anti - tank ammunition meant that each weapon was only supplied with six or seven rounds . A number of Smith Guns were also issued to regular army units tasked with guarding airfields , and one was even mounted onto a Bren Carrier , although this prototype did not go into production . Despite the problems with the weapon , and its tendency to injure or even kill those who manned it , the government attempted to portray it in a positive light , issuing special instructions in the autumn of 1942 which stated that the Smith Gun was a " simple , powerful and accurate weapon which , if properly handled , will add greatly to the firepower of the Home Guard . " After a period of initial distrust , many Home Guard units appear to have taken to the Smith Gun and attempted to make the best use of it . Mackenzie states that some units even had ' a growing sense of affection for the weapon ' and describes how , when a letter was published in The Times towards the end of the conflict criticizing the weapon , numerous Home Guard volunteers replied with their own letters describing how satisfactory the Smith Gun had been ; they also stated that it was " one of the best pieces of equipment ever issued to the force . " No Smith Guns were used in active service , and they were declared to be obsolete in 1945 .