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Charlton Automatic Rifle
By Jean Huon

When Great Britain and its associated commonwealth nations and colonies were drawn in to World War II, their infantry weapons were standardized but were characterized by a lack of automatic guns at the individual level. The most outstanding initiative to fill this gap came from Great Britain with the Sten submachine gun; but it would be unjust to neglect the efforts carried out by two dominions attached to the Crown: the Owen submachine gun in Australia and the Charlton automatic rifle in New Zealand. It is important to note that these two achievements were due to private initiatives.

The Charlton rifle is a selective fire automatic weapon produced from parts of old Lee-Metford and Lee-Enfield repeating rifles. It is not strictly a transformation, but the occasion of the re-employment of remodeled weapons. The idea and the development of this rifle came from a mechanic from Hastings, New Zealand: Philip Charlton.

In 1941, Philip Charlton presented his prototype to the New Zealand Army. After various tests, the weapon was adopted on November 7, 1941 and its production was undertaken; but it is there that difficulties started. The raw material, i.e. repeating rifles of the old model, was provided by the military authorities. Refurbishment or manufacture of various elements was entrusted to subcontractors, and final assembly was carried out by Charlton's Ltd. factory located on Nelson Street in Hastings.

Difficult beginnings

From prototypes to final version, some improvements were made, but the Army demanded guns with interchangeable parts. That seemed to be a normal request but was difficult to do because of the problems encountered by the manufacturer. It is regrettable to note that the New Zealand military authorities did not seek to facilitate the task of the manufacturers, nor to take seriously the weapon which had been produced. These facts were the subject of a scathing report written by the deputy controller of the Ministry of Supply and addressed to the Staff of the armed forces in Wellington, on August 13, 1942. The controller raised the following facts: At the end of 1941, Ordnance provided to the Charlton factory the first batch of 237 Lee-Metford rifles of the model agreed upon for the transformation. When supplies of this weapon were exhausted, it was replaced by the Lee Enfield Mark I rifle. These two weapons not being exactly identical, it was difficult to convert them using the same blueprints. The date of manufacture of rifles which were finally delivered ranged from 1889 to 1903, which included the following models:
  • Lee-Metford Mark I and Mark I*,
  • Lee-Metford Mark II and Mark II*,
  • Long Lee-Enfield Mark I and Mark Mk I*, those coming from three different gun factories.

To limit these disadvantages, it was requested that the Army deliver rifles at a rate of 200 rifles of the same type every month, which corresponded to the production capacity of the Charlton factory. But this request was not acted on and as of the date when the report was written:
  • in December 1941, 257 Lee-Metford rifles were delivered, of which 20 were returned because they were still considered to be “good for service” and were available for issue to troops, which brings us back to the figure of 237 rifles referred to above,
  • In March 1942, 100 Lee Enfields were delivered with 75% of them were suitable for instruction only. All rifles were carefully checked and some surprises awaited the technicians of Charlton's Ltd.

Material

Barrels: Approximately 50% of the original barrels were badly fouled or worn. An additional 200 barrels were supplied to replace them and an inspection, gauging and reconditioning process was incorporated to rescue a sufficient number of barrels to make up the quantities required. This proved to be quite satisfactory.

Bolts: Due to the shortage of bolt head gauges it was found to be very difficult to set the cartridge headspace to Army inspection requirements. To overcome this, the original bolts were re-machined and heat treated and the bolt heads were refitted to give correct head space.

Cocking pieces: This highly stressed part had in many cases become badly fatigued, and it was found impossible to recondition them by heat treatment. An analysis showed flaws developing so that it was considered advisable to make and fit a new part to every rifle. Parts used in the newer models of rifle were unprocurable even in Australia. The steel in this part gave considerable trouble in hardening and it was only after considerable experiment that the difficulty was overcome.

Firing springs: The strength of these springs had become considerably reduced in the older rifles to the extent that they caused misfires. Re-tempering by a springs specialist in Wellington proved unsatisfactory, so a vibratory pneumatic hammer was adapted for conditioning after re-sizing. This process was eminently satisfactory and no further trouble was being experienced with the re-vitalized springs.

Bolt heads: Early breakages proved some of the bolt heads fatigued but an examination showed them to be made of basic iron and a few hours heat soak and subsequent heat treatment overcame the weakness and the reconditioned parts tested now equaled the parts from standard weapons.

Receivers: Wide variations in hardness were experienced in these parts and were overcome by spot annealing and grinding where softening was unadvisable. The finished losses on this important part were less than 5%.

Steels: Trouble was experienced very early in the contract due to the inferior types of mild steel used in place of the imported article no longer easily procurable. Even the bright rolled types show scale entrapment and hard sections incapable of being accurately turned or bored. Some sections of 1 1/4 bright round proved to be up to .015 out of round and badly scaled, necessitating machining all over. Angle iron locally rolled proved to be of badly varying tapers on the inner sides and involved much machining. The small quantities of high tensile steel required for the gas ports were unprocurable and a substitute was made by annealing old automobile valves. Some sections of mild steel were still unprocurable and recourse had to be made to the use of shearing sheet, arc welding and bending.

Cams: Manufactured by Machine Tools Ltd., Wellington. This was a basically intricate part, which to be correctly manufactured would involve the use of a profiling mill and drop hammer. Considerable difficulty was experienced in fitting the part as supplied and difficult hand work was involved in finishing the first two batches of 100. Later materials were much easier to fit and involved only approximately twenty minutes per part.

Springs: Made by N.W. Thomas & Co. Ltd., Wellington. The first batches of springs were hand made and required individual fitting, but the final batches were quite satisfactory. Trouble was experienced due to the variations in strength of the 14-inch retractor spring but this was overcome by means of individual setting. Spring stock of the correct gauge was unprocurable and modifications were made to enable lighter gauge material to be used.

Cooling fins: Produced by Precision Engineering Co. Ltd, Wellington. The first batches were hand made and required individual fitting. Later types could not be stamped to specifications as deep drawing sheet steel was unprocurable. The trouble was overcome by using thinner material and double quantities of fins which in turn necessitated the construction of a machine to press the pairs on to the barrels.

Trigger side plates: Produced by Precision Engineering Co. Ltd, Wellington. Delivery was delayed.

Side plates: Made by Motors Mowers Ltd., Hastings. Very considerable difficulty was encountered both in the manufacture and fitting of this part, due chiefly to variation in the breech body of the rifle and in part to the material available for its construction. The type of angle iron supplied proved very inaccurate, undersized, expensive and difficult to machine. It was discarded in favor of welded flat bar. The drilling and location trouble was overcome and it was possible to lower the manufacturing costs of 12 shillings 3 pence to only 3 shillings.

Cocking pieces: Made by Motors Mowers Ltd., Hastings. Here was encountered trouble as it was found that steel in the correct size suitable for perliton hardening was unprocurable and a lengthy hold up was caused by endeavoring to use silico-manganese spring steel, which was finally proved to be unsatisfactory due to spot hardening difficulties. The trouble was overcome by cutting parts from mild steel bar and refining the core by heat treatment after case hardening.

At the end of his report, the Squadron Leader Munitions Controller concluded: "It will be seen from the above report that many of the difficulties experienced have been largely beyond our control, but they have been overcome to a point where a dispensable, rigidly tested weapon has been produced, and in spite of the set-backs a commendable effort has been maintained by the organization. The lack of co-operation of the Army Authorities is a disappointing feature and it is most discouraging to find that of the 25 original training weapons built by hand, 12 are still lying at the local Drill Hall and have never been issued from there, and of the rifles used in training which gave cocking piece trouble, none have been returned for correction or examination despite numerous requests."

Improve

It is obvious that such a report could not leave the New Zealand Staff indifferent and it is probable that various responsible persons were punished. Thereafter, the delivery terms seem to have improved and a total of 2,000 Charlton automatic rifles were manufactured.

At the beginning of their delivery, these weapons were looked on as light machine guns and were used as such for training. However it had been planned to employ them in combat units as semiautomatic rifles. Full auto fire was kept for emergencies to keep a reserve of firepower within the unit.

The instruction manual showed shooting in three positions:
  • from the bipod,
  • from the waist,
  • from the shoulder

But finally, the Charltons were distributed to the Home Guard and never saw combat.

The Charlton Automatic Rifle was a heavy and cumbersome weapon. But it is a particularly interesting initiative. One can only bow before the ingeniousness of the inventor and his determination to overcome the innumerable difficulties encountered during manufacture. Although never having been used as such, the Charlton was one of the first assault rifles.

Characteristics Charlton

Cartridge .303 British
Overall length 1.150 m (45.27 inches)
Barrel length 0.650 m (25.59 inches)
Weight without magazine 5.950 kg (13.13 lbs)
Magazine capacity 10 or 30 rounds
Cyclic rate 700 rpm

Description

Barrel group: On the muzzle of the barrel are fitted the compensator and the blade type foresight with protectors; half way along the barrel is fitted the folding bipod adjustable telescopic legs, and the bipod stop. Behind the bipod bracket is fitted the gas port and behind this the radiator to which is fitted the leaf and slide type rear sight. Underneath the barrel is the fore grip and behind this the shield. On the right of the barrel and fitted to the gas port are the gas cylinder and return spring tube.

Body group: The body group consists of:
  • The piston, connected to the return spring rod and to which is fitted the bolt operating arm with cam slot and cocking handle, the piston guide and stop, which guides and supports the piston during its backward and forward movement and limits its backward travel.
  • The modified rifle bolt with its actuating stud and the projection for automatic firing.
  • The bracket to which is fitted the operating arm catch, the rear cross piece with bolt and cocking piece stops and the rear cross piece keeper screw.
  • The modified rifle receiver with ejector.
  • The left and right trigger mechanism covers with their magazine guides. On the left cover is fitted the selector which may be set at either: Safety, Repetition, or Automatic.
  • The magazine catch, trigger, trigger stop and trigger guard, behind which is fitted the pistol grip.
  • The butt.

The rifle is fed by a Lee magazine holding ten rounds or a Bren 30 shot magazine.

Operation

To load, set the change-lever at Safe. Place a filled magazine in the rifle, pull back the cocking handle and let it go. The rifle is now loaded and ready to fire. To fire, set the change lever at R or A, aim and press the trigger.

Backward movement: When a round has been fired, the gases following the bullet up the barrel pass through the gas port into the gas cylinder where they strike the piston and force it to move to the rear. The cam slot in the operating arm, bearing against the actuating stud on the bolt, turn the bolt to left, unlocks it and forces it to the rear. The piston has traveled about one inch to the rear before the bolt is unlocked. As in the service rifle, as the bolt is turned to the left, primary extraction occurs and the striker is withdrawn from the primer and the empty case is eased slightly from the chamber. When the actuating stud has reached a vertical position, the bolt is unlocked and free to travel to the rear. The extractor claw gripping the rim of the cartridge case, extracts the case from the chamber. As the bolt travels to the rear, the base of the cartridge case comes up against the ejector which forces the case off the face of the bolt and throws it clear of the weapon. The piston and bolt then travel fully to the rear until they come up against their respective stops. The return spring is compressed during this backward movement.

Forward movement: The piston and bolt having reached the backward position, the piston is forced forward by the return spring and brings with it the bolt. During this movement the face of the bolt engages behind a round in the magazine and forces the round into the chamber. As the operating arm drives the bolt forward the cam slot is endeavoring to turn the bolt to the right and lock it. This locking occurs when the rear end of the rib of the bolt has cleared the front end of the resisting shoulder, when the bolt is turned to the right and locked. During the forward movement of the bolt the sear engages the bent of the cocking piece and holds it in the cocked position until the bolt is locked and the sear depressed.

Firing mechanism: With the change lever set at S, the safety catch prevents the trigger from being pressed. With the change lever set at R, on pressing the trigger the sear is depressed and the cocking piece is allowed to go forward. As the cocking piece moves forward, the bent strikes the trip lever and moves it forward, thus disengaging the sear from the trigger and allowing the sear to rise again ready to engage with the bent of the cocking piece when the bolt moves forward again. With the change lever set at R, the trigger must be pressed and this action repeated before the next round can be fired. With the change lever set at A, with the bo1t fully locked and the action cocked, the sear plunger is disengaged from, and the trigger engaged with, the sear. On pressing the trigger the sear will be depressed and the cocking piece will be allowed to go forward. After depressing the sear, the trigger will disengage from it and will remain disengaged for such time as the trigger is kept pressed. On the bolt turning to the left after a shot, the sear plunger and sear will be allowed to rise as soon as the cocking piece has moved sufficiently far enough to the rear to allow this to happen. The sear will then engage with the bent of the cocking piece as the bolt moves forward again. When the bolt is turning to the right after moving forward, the projection on the bolt will depress the sear plunger, which will in turn depress the sear and allow the cocking piece and striker to move forward and fire the round. On releasing the trigger it will engage with the sear and the sear plunger will be lowered to a position where the projection on the bolt cannot strike it. The sear will therefore not be depressed and the rifle will stop with the action cocked.

Stripping and Assembly

To remove the bolt: Remove the keeper screw and raise the rear cross piece. Push the operating arm catch to the left, half pull the cocking handle about a quarter of an inch to the rear and raise the operating arm over to the right. Pull the bolt to the rear, raise the bolt head and withdraw the bolt.

To replace the bolt: Set the change lever at R. Ensure that the cocking piece is in line with the resisting lug and that the bolt head is screwed home. Place the bolt in the body and push forward until the head is clear of the resisting shoulder, turn the bolt head over to the right, push the bolt forward and lock it to the right. Engage the actuating stud in the cam slot in the operating arm and fasten the operating arm. Lower the rear cross piece and secure it. Pull the cocking handle back two or three times to ensure the moving parts are working correctly. Press the trigger and set the change lever at Safe.

To remove the piston: Remove the nut on the end of the return spring rod. After raising the guide pawl, unscrew the piston rod guide and remove it from its bracket. Pull the piston to the rear leaving the return spring rod forward; remove the piston forwards.

To replace the piston: Reverse the order for removing.

To remove the return spring assembly: If the piston has not already been removed, remove the nut of the end of the return spring rod. Remove the nut on the front end of the gas cylinder. Remove the return spring assembly to the front.

To strip the return strip assembly: Separate the tube at the collar by pulling the two portions apart. The collar is fixed to the smaller portion of the tube. Depress the spring and sleeve on the rod and remove the ring clip. Remove the spring and sleeve.

To replace the return strip assembly: Assemble in reverse order.

Variations

“Electric” Charlton: Experimental weapon whose mechanism is moved by an electrical motor.

Charlton Electrolux: Model made by Electrolux in Melbourne in Australia. The general design of the weapon is simpler. Conversion is carried out starting from Lee-Enfield No 1 Mark III*. The front part of the barrel receives a perforated cooler. On both sides of breech, two plates are installed. The right-hand plate covers the operating arm, the left supports the selector. The stock was redrawn and it received a pistol grip. The sight was an aperture located to the back of the breech. This model remained in an experimental state.

Charlton Howell: Another alternative carried out in Great-Britain starting from Lee-Enfield No 1 Mark III*. One had planned to equip the Guard Home with it for the anti-aircraft defense, but the project was not completed.

Most of the Charlton rifles were destroyed by an accidental fire after the war. Some rare specimens remain in museums. At the beginning of 2011, the New Zealand company New Gun City proposed one of them for sale at the price of 10,000 New Zealand dollars (USD $ 7,800).

Grateful acknowledgements are given to the following for their invaluable help in researching this article:
  • New Zealand Ministry of Defense. The public relation officer and his assistant, Staff Sergeant E. A. Black.
  • National Army Museum Te Mata Toa, Mr. Terrence Seymour, Assistant Curator Weapons, Waiouru (New Zealand).
  • National Firearms Collection (Royal Armouries), Leeds.
  • Mr. Régis Calazel.
  • Mr. Richard Godin.
  • Col. Colin Doane (Rtd).

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