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The Enduring Bren Gun

The Enduring Bren Gun
This Czech-Designed Light Machine Gun
Served The Commonwealth Well From
1935 To 1999.

The light machine gun concept proved its tactical worth during WWI and led Britain to develop the Bren gun. It replaced the heavy, complicated Hotchkiss Portable and Lewis machine guns, which saw widespread use by the Allies. The ultimate LMG during WWI proved to be the much lighter American Browning Automatic Rifle, which fed from a box magazine rather than the long, fragile Hotchkiss strips or Lewis drums.

In the early 1920s, the Browning BAR was clearly superior among existing designs in the British search for a light machine gun, but the search continued for something better. During the 1930 light machine gun trials, arms from around the world, including the Browning BAR, were tested. The eventual winner, the Czechoslovakian Brno-made 7.92mm Lehky-Kulomet ZB27, underwent further refinements, not the least of which was the conversion of the plans from metric to “inch” and modifications to fire the rimmed .303 British instead of the rimless 7.92mm (aka 8mm Mauser).

Named the ZGB during the refinement period, contracts and royalties were agreed to with Brno in 1935, and manufacturing began at Royal Small Arms Factory Enfield. The new gun was now designated “Bren” after the “Br” in Brno and “En” in Enfield. Production Bren guns started rolling off the RSAF Enfield line in 1938. With war looming, the Bren was going to be in short supply. Wise heads contracted with the firm of John Inglis in Canada to also manufacture Bren guns, and the firm quickly ramped up to produce Brens alongside other war material and heavy machinery. Inglis-made Bren guns started coming off the assembly lines in 1940.

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The front sight is offset in a bracket welded to the stainless steel
barrel sleeve, itself pinned to the blued, carbon steel barrel. The
front sight came in five different heights to adjust elevation and
was drift adjustable for windage. The Mk I bipod allows the gun to
be tilted right, left and traversed a few degrees without moving the legs.

Manufacture

The Bren was a complicated gun to build, with nearly every part machined from a forging. Those were the days when just about everything was made in such a fashion, and a little more than 83,000 square feet of the 220,700 square-foot John Inglis plant was dedicated to Bren manufacturing. In a Toronto Telegram newspaper article dated April 10, 1940, Staff Reporter Percy T. Cole wrote, “…the Bren gun starts as unshaped pieces of metal weighing at the outset 101 pounds. When they finally get through the 2,846 separate operations that are required to make a finished gun, the metal parts weigh 18 pounds. That gives some idea of metal that must be removed to measurements as low as one ten-thousandth of an inch.

“There are 17,604 fixtures, tools and gauges required […] to produce the 161 separate parts of a Bren gun. There are 15 entirely different alloys of steel required and each of these alloys is special. They must therefore be produced and examined under the expert guidance of a metallurgist. Practically every steel component of the gun requires some special form of heat treatment and several of the parts are finished with a process known as ‘browning.’ That is, the shiny parts are ‘rusted’ so they won’t give off reflections of light, and possibly betray the presence of the operator in the field to the enemy.”1

While manufacture itself was complicated, the Bren was far easier to fieldstrip than the Hotchkiss and Lewis guns. The Bren gun’s disassembly begins by pulling out the body-locking pin, which can be started easily with fingers or the nose of a bullet and is captured in the receiver to prevent its loss. Disassembly for simple cleaning and oiling requires only a slight assist from the issued tool wallet. Hardest to clean was the buildup of carbon and corrosive fouling deposited by WWII ammunition. Unlike today, solvents to dissolve carbon were unknown, and the heavy fouling had to be scraped away.

The barrel has a quick-change feature and two fitted barrels were provided with every gun. The adjustable gas system’s four progressively larger apertures were locked into place when the barrel was mounted. As the gun became progressively dirtier, the gas nut could only be turned during barrel changes and a wrench was included in the tool wallet. It was recommended the barrel be changed after every three or four magazines. Whether that was practical in the field is another matter, but it could be accomplished fairly rapidly.

The early guns had problems with carbon fouling. Of the 30,000 in inventory at the war’s start, 27,000 were lost or abandoned by troops at Dunkirk, France, in 1940.2 Likely, the Bren didn’t receive the gas system cleaning necessary to keep it running, not surprising since the BEF had to move fast in the face of Germany’s Blitzkrieg. Modifications to the gas system helped, and production sped up by simplifying some aspects of the Bren’s complicated machining. The shortcuts were mostly cosmetic, and all internal parts between the different models still interchanged.

Brens simplified at RSAF Enfield were called “Mk I (modified)” but the name on the receiver was still just “Mk I”. John Inglis of Canada marked ones made there “Mk Im”. The difference in the receiver machining between the Mk I and Mk Im is readily apparent to the eye, with the Mk Im having a flatter, smoother receiver.

The subject of this story is a Bren Mk Im made by John Inglis in 1943 and converted to semi-auto by Wise Lite Arms of Boyd, Texas. When I first examined my Bren, purchased on www.gunbroker.com, I was struck by how sturdy the construction was, and how intuitive the basic operation of the gun is to load, charge and fire. Simply open the dust cover on top, hook the front of the magazine into its recess and rock it back until it latches. Pull the non-reciprocating charge handle all the way to rear (which automatically opens the bottom dust cover if it’s closed) and let it fly. The 3-position safety lever is just above the pistol grip on the left side of the action (now a 2-position safety after conversion to semi-auto). To change magazines, push the big thumb latch forward to lift the
magazine free.

The disassembly goes smoothly as well, although a few points of it are different because of the semi-auto conversion. The internal parts are big, sturdy and most not easily lost if taken apart in the field. These guns were fired with corrosively primed ammo, so it was important they be easily maintained. (Of course “easily” is defined by 1930s’ standards. Modern cleaning solvents make this chore a snap.)

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The little shooting spot Jeff uses in the desert has targets set up
halfway up the hillside and the AA setup of the folding tripod is
perfect for plinking there. Note that for this photo the rear sight
is set for 2,000 yards — its highest setting — showing how much drop
the old .303 has. The gun pivots freely on the arm in this position.
A zipper beneath the bag dumps the empties.

BREN-400

The John Inglis-built 1943 Mk Im Bren gun in .303 British sits atop
an original Mk I folding tripod overlooking the Northern Nevada desert.
Rebuilt into a 922(r)-compliant semi-auto by Wise Lite Arms, the torch-cut
receiver was welded and the action converted to shoot from a closed bolt.

Mobility

The Bren gun and spare barrel were shipped in a wooden transit chest with all the tools required for maintenance. In keeping with the mission of mobility, the transit chest would be left behind, and the assistant gunner would pack a canvas bag called a “holdall” with the spare barrel, and fill the holdall’s external pockets with tools. A canvas “tool wallet,” which could be slung separately or stuffed in the holdall, included a pull-through to clean the barrel, combination tool, spare parts (extractor, spring and firing pin), oil bottles, scrapers and patches. The wallet was light, compact and if slung, its pocket in the holdall filled with a spare magazine. Brushes, mops, a short wooden rod and long 1-piece T-handle rod for cleaning the gas system and barrel stayed in the chest.

The assistant gunner carried a steel magazine chest with twelve 30-round magazines. The magazines had to be carefully loaded so the rim of each .303 cartridge was in front of the one deeper in the mag, and it was recommended only 27 rounds be inserted into the magazine to ensure reliable feeding. The British designed several different magazine-loading tools, but they were rarely employed and today are quite scarce.

While two men were usual in the Bren team, the gun was deployable by one man, who could pack extra mags in his web gear. The assistant gunner had quite a load, carrying 12 mags in the steel can, at more than 32 pounds in one hand in addition to the spare barrel, tools and his rifle and kit.

As originally envisioned, one out of every four guns was issued with a 30-pound tripod made from hollow steel tubes for use as an emplaced gun for defensive operations in the role usually served by a heavy machine gun. The tripod’s articulated legs allowed for great flexibility in laying the gun. At the rear, the buttstock locked onto a horizontal traversing mechanism on a steel arc with a scale. The traversing mechanism had a wheel for fine elevation adjustments.

Early Mk I tripods also had two arms stored in the hollow tubes to elevate the gun high enough for use as an anti-aircraft gun. A canvas bag could be fitted underneath to catch empties from the bottom-ejecting Bren, a useful accessory when the Bren was mounted in the AA position or on a Bren Gun Carrier. The bag had a large brass zipper underneath to dump the empties. For transport, the tripod folded flat, had two rifle slings and could be carried by one man like a backpack.

bren5

Friend Roger Renner shoots the Bren, using the sling for support.
On the move, the Bren was fired from the hip in this fashion.

Wise Lite Arms Conversion

To be imported into this country, the Bren gun’s receiver was torch-cut in three places. Since the 1986 revisions to the 1968 Gun Control Act forbade any manufacture of new select-fire or fully automatic firearms for civilian use, these parts kits couldn’t be used to restore a Bren to its original select-fire operation. But they could be turned into semi-auto versions of the gun if the semi-auto design was incapable of accepting the full-auto parts.

Welding the receiver is a difficult task, requiring a jig to maintain alignment, with the inside of the receiver having to be machined again to allow the bolt to operate. The new design converts the gun to fire from a closed bolt rather than the original open bolt, and Wise Lite had their design approved by the ATF. In addition, in accordance with current law, only 10 original parts enumerated on a list may be used, so Wise Lite made enough new parts to keep the gun in compliance. Wise Lite put in a new magazine follower and base plate in order to use other original parts. Compliance with the law is an odd dance.

The chap I bought this Bren from admitted he only fired a few rounds and put it away. The gun was dry, so a thorough cleaning was first. The Bren’s barrel was very tightly fitted and careful tapping with a brass-tipped wooden rod and a hammer was required to loosen it. A rubber mallet helped get the upper and lower apart. I cleaned the barrel with Barnes CR-10 and oiled the action with Shooter’s Choice FP-10. Once oiled, it went back together far more easily, although the barrel had to be tapped into place. In a rare fit of common sense, I turned the gas system nut to its smallest aperture before reassembly.

This Bren is set up with all the accessories a Mk I would’ve sported, including the buttstock handle, the Mk I bipod with extending legs and the folding tab on the buttstock to keep the gun indexed at the top of the shoulder in the firing position. While all these complicated assemblies seemed like great, functional ideas in peacetime, wartime required simplification to speed up production. I imagine the buttstock handle was thrown away the first time a gunner survived having it snag crossing wire or a fence, although the shoulder tab and bipod are useful.

When fitted with the Mk I bipod, the Bren sling has two snap rings used to attach the sling to eyes in the butt and on the bipod. The sling attaches to the left side of the bipod and right side of the buttstock. The gun wasn’t meant to be slung like a rifle, but used over the shoulder to support the gun when fired from the hip. Carried by the handle, the muzzle is oriented slightly up rather than at the balance point of the gun. Since the gunner’s mates would be out in front as a rule during movement, this keeps the muzzle pointing over their heads instead of at their backs.

bren6

The long, spongy Bren 7-pound trigger pull can be a trial shooting groups.
Never meant to be a target rifle, the best 5-shot group Jeff got was 3.625″
(four shots in 2.375″) in spite of high winds.

bren4

Bren guns came in a wooden transit chest designed to withstand the
rigors of harsh travel. The chest contained everything the gunners
required for shooting and maintenance, including one fitted spare barrel.

Shooting

For the first range test, I shot Precision Cartridge Inc. .303 topped with Hornady 174-grain FMJ bullets and some horded, treasured PMP Mk VII ball from South Africa proven accurate in other .303 rifles. Both cycled the action smoothly and easily.

Shooting from the bipod off the concrete bench at the Washoe County Range was a little problematic since the bipod put the gun just a little too high. The group with the PMP ammo was decent, albeit low. Zeroing the Bren for elevation was originally accomplished by changing the front sight height. To be correct, the gun should shoot 1.5″ high at 100 yards with the back sight set at its lowest position of 200 yards.2 Since this one shoots a couple of inches low, I’ll search around for a lower front sight. I can always turn up the backsight for now. It’s very quick to use, adjustable in 50-yard increments out to 2,000 yards.

No stoppages occurred in firing several hundred rounds. I cleaned and wiped away the carbon buildup with M-Pro 7 — much easier than using the issued scrapers. After the second range session, newly-acquired Hoppe’s Synthetic No. 9 solvent removed the carbon buildup just
as quickly.

During the second range session, I placed a white Birchwood Casey Shoot-N-See target at 100 yards. My best 5-shot group was 3.625″ (4 shots in 2.375″) and 10-shot groups enlarged to about double. It was windy, so I shot the 5-shot groups rather quickly, trying to keep the conditions the same. For fun, I loaded the magazine with PCI ammo, raised the sights and fired at the gongs placed at 250 and 400 yards. I was able to reliably hit the 250-yard steel eight out of 10 tries, but only managed to strike the farthest gong twice out of 10 shots. An early complaint with the Bren was it was too accurate. Likely true, and no doubt the tight barrel fit provided by Wise Lite is why mine still shoots this well.

The semi-auto mechanism as designed by Wise Lite uses a striker to hit an inertial firing pin inside the now-closed bolt system. The striker is heavy enough to give the rifle the feel you are firing from an open bolt as it flies forward to strike the firing pin. The trigger pull is a long, spongy 7 pounds, traveling quite a distance before it lets go. If you concentrate on holding the sight picture, the trigger is not unmanageable considering the gun with full magazine weighs 25 pounds, 11 ounces.

The Bren gun has proven to be a great deal of fun to shoot. While quite a load for casual desert plinking sessions, a well-fit barrel in good condition is decently accurate, allowing for long-range hits. The Bren is a nifty and rare addition to any WWII collection of Allied arms.


Fieldstripping

The Wise Lite Bren has a very tightly fitted barrel. First, ensure the rifle is unloaded and leave the action cocked with the safety on. Close the magazine dust cover. Lift the barrel nut catch and remove the barrel straight forward. If necessary, gently tap the barrel forward using a brass punch and small hammer on either side of the gas port

bren10

The bipod can only be removed when the barrel is out. Holding both legs together, give it a quarter turn to the left and remove it forward. To separate the receiver from the trigger group, push out the pin located at the top left of the receiver. Pull it out until it stops. It is captured and can’t be removed. Now slide the trigger group and buttstock out to the rear.

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Start it moving by tapping the triggerguard with a rubber mallet. Note the striker is held in place by the sear. Pull it back and up to remove it. The striker spring is longer than its rod. Restrain it so it doesn’t fly.

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The gas piston and bolt slide out from the back of the receiver.

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Separate the bolt from the gas piston assembly (the gas piston will need no further disassembly for cleaning). Push the firing pin restraining pin out to the right and remove the firing pin from the rear (note the tip is rectangular in shape — this is correct). Pull back and lift out the extractor stay and spring. Lift the extractor up straight.

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Turn the gas nut on the barrel until it aligns with the slot in the barrel. Push it out (if fouled, it may need to be tapped out). Clean the gas system parts with a modern carbon-removing solvent like M-Pro-7 or Hoppe’s No. 9 Synthetic.

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The Bren fieldstripped into its major components with a Mk II bipod.

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Reassembly is straightforward. Be careful you don’t kink the striker spring reinstalling it into the butt. The striker will keep it in place once it’s caught by the sear. The Mk I barrel has a female dovetail that mates with a corresponding male dovetail on the receiver. Be sure it slides onto the dovetail as you are reinstalling the barrel. Otherwise the barrel alignment will be crooked and it’ll jam as you try and seat it.


Into Battle

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The transit chest would be left behind as the troops advanced. The assistant gunner would stuff the spare barrel into the “holdall” (1) along with the tool wallet or a spare mag (the tool wallet could be slung separately). The wallet held a variety of tools to manage the Bren including an oil bottle (2). Introduced in 1946, a gas system fouling scraper hand stamped “TOOL FOULING BREN MKI” finally gave gunners a scraper to deal with carbon buildup inside the gas tube (3). In the metal tin (4) were spare springs, broken shell extractor, spare extractor and spring and spare firing pin and spring along with metal gauze for cleaning carbon. The key ring (5) holds differently-sized scrapers to clean the gas regulator’s four holes. Just above the scrapers is the combination tool (6) with various locking screwdriver types, gas wrench, and on the other side is a copper-headed hammer. Below is the barrel pull-through (7) and finally, the tool wallet itself (8), which held all this stuff in separate compartments along with a larger oil bottle.

You had to be fit to be an assistant gunner. In addition to his regular gear, the wallet weighed 2 pounds, 5 ounces, and the holdall with barrel and wallet weighed 9 pounds, 10 ounces. His SMLE No. 1 Mk III rifle weighed 10 pounds and a loaded magazine chest roughly 32 pounds. Quite a load!

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The transit chest held more solid and aggressive tools for cleaning the Bren. Atop the tool wallet is the wooden rod with its mop attached and its wicked looking steel brush for scouring the gas system. Later in the war, a 1-piece T-handled steel rod was included in the chest, yet the cord pull-through in the tool wallet was used in the field.
By Jeff John

Notes:
1 Toronto Telegram story courtesy
Canadian War Museum
1 Vimy Place
Ottawa (ON) K1A 0M8
Canada
(800) 555-5621
www.warmuseum.ca

2 The Bren Gun Saga, by Thomas Dugelby, revised and expanded edition edited by R. Blake Stevens, ©1999, OP, Collector Grade Publications Inc., P.O. Box 1046, Cobourg, Ontario, Canada K9A 4W5, (905) 342-3434, www.collectorgrade.com

For more info

Birchwood Casey
7887 Fuller Rd., Suite 100
Eden Prairie, MN 55344
(800) 746-6862
www.birchwoodcasey.com

Hoppe’s (Bushnell Corp.)
9200 Cody
Overland Park, KS 66214
(800) 423-3537
www.hoppes.com

M-Pro 7
225 W. Deer Valley Rd.
Phoenix, AZ 85027
(888) 608-7888
www.mpro7.com

Precision Cartridge, Inc.
940 Georgiana St.
Hobart, IN 46342
(219) 942-2400
www.precisioncartridge.com

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  1. Ian Hannant says:

    Looking at your man firing the BREN from the hip – he’s going the right way towards burning his hands on the ejected cartridges! That’s what the carrying handle’s for…

  2. The spent cases eject out the bottom under the magazine. Roger faces a danger of slipping on the empties more than being burned. It is awkward to try and shoot using the carry handle in this position even though the arm is slung.

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