Differences In Component Assemblies

Many guns were upgraded in service with various replacement parts and ensuing Marks of barrels, bipods, butts, &c. Assemblies from the different factories may also be fitted.

The body Mark number is found on the receiver, with the factory name or code and year of production. Most parts and groups are interchangeable on the various action bodies. A code system was applied in Britain during W.W.2 for commercial contractors and stamped on many parts. Enfield guns usually have the "E" logo while the Monotype guns are coded M67 or "D" for Daimler. Canadian receivers can be readily identified as they are marked "INGLSS"; their Australian counterparts are stamped "LITHGOW" and "MA". Indian receivers are usuaily marked "SAF", Gun serial numbers are usually found at the top rear of body, left side of barrel, rear of butt-slide and on the barrel nut.


Bren Mark Iii

Action bodies from top: Mk 1 Enfield (1937), Mk 1(M] Lithgow, Mk 2 DaimlerlMonotype, Mk 2f1 (originally Monotype), Mk 3 Enfield and Mk 4 conversion. Note differences in body cuts & lightening, backsights, gas vents & milling, and harrel cradles. Mk 1,1(M) & 3 bodies have locating lug (rear of gas shield) to centralise barrel. Mk 2 & 4 bodies do not. Barrels Mk 1,1* & 3 have a corresponding slot behind the gas block to fit Mk 1,1(M) & 3 bodies. While reported that Mk 2,4 & 5 barrels are not interchangeable onMk 1 & 3 bodies, our experience is that all barrels interchange on all Mark bodies. - M.O.D. Pattern Room.


Butt Mk I. Cupped buttpiate; early model had folding butt strap and butt handle. Production economies dispensed with the folding butt strap and handle.

Butt Mk 2. Flat buttpiate with extended shoulder rest. Recoil spring and plate omitted, new butt swivel and plate fitted. Return spring retained by a screwed spring tube nut.

Butt Mk 3. Further production economies to Mk 2, with flat buttpiate heel; not issued.

Butt Mk 4. Lightened and tapered, sling swivel bar on buttpiate with recess slot.

Bren Light Machine Gun

From the left— Butts Mark 1, 2, 3 and 4. M.O.D. Pattern Room, Nottingham.


Marks 1, 2 & 3. Machined from solid, the new Marks progressively simplified manufacture. Major differences are obvious from the drawings; the progressive machining changes are not necessarily related to specific marks of the butt slides.

Cocking Handle:

Mk I. Spring-loaded and hinged cocking knob, folds forward in the closed position and does not reciprocate with the butt slide during operation. Gives a thinner gun profile.

Mk 2. Fixed handle and plunger; it does not fold forward like the Mk I pattern.

Mk I. Lightening recess on outside of side ¡ever. Safety cam on underside prevents butt being fully withdrawn and mechanism cocked or fired, unless the nut is fully closed.

Mk 2. Safety cam omitted. Lightening recess also omitted, a production economy.

Mk 3. Slightly different machining, only uses the catches Marks 2 or 3.

Gas Piston & Post:

Mk I. Comprises stem, extension, piston post, piston post spring, plunger, cotter and pin. Fluted piston stem. Mk 1 piston post is not as deeply recessed, larger in diameter,

Mk 2. Mk 2 plunger is longer, the Mk 2 piston post is recessed deeper and is smaller in diameter, giving better support to the plunger and surrounding spring. The piston stem is not fluted.

Light Machine Gun
Magazine Catch:

Marks 1 & 2. Mk 1 catch has a milled recess in the rear face of the thumb-piece; the Mk 2 has a hole bored through it.

Barrel Nut:

From left-Marks 1, 2

From left-Marks 1, 2


Mk I Assembly. Usually without a Mark designation number. It is 25-in. long with a stainless steel sleeve for the last 10.5-in. to muzzle. Straight taper on flash hider, so it is similar to the Mk 1* except for the external taper of the flash hider cone.

Mk I* Assembly. Stamped "I*" on left side near breech. Mk III gas regulator fitted, with its larger three gas vents increased in diameter, stamped "[11". Some Mk I barrels were converted to this pattern (also 25-in. long). Distinct "kink" in flash hider cone taper.

Mk 2 Assembly. Flash eliminator and gas block fit onto barrel end, not integral with it. Eliminator incorporates foresight bracket, gas block houses the regulator. No locating recess tongue (near the middle} underneath the barrel; 25-in. long.

Mk 4 Assembly. Lighter construction, new design flash eliminator and foresight block; 22.25-in. iong. {Mk 3 was 2-groove experimental only).

Mk 5 Assembly. Lighter construction, modified Mk 2 production by turning down and shortening. Longer sighting radius, sighting bracket closer to muzzle; 22.25-in. long.

Different barrel marks, from topMark 1\ Mark 2, Mark 4 and Mark 5. Note the different barrel lengths, forms of the foresight and their positioning, which affects relative sighting radius. Carry handle sleeves; Mk 1 has lightening holes, Mk 2 has none, Mk 3 is shorter with lightening holes. Waisted Mk 1 wood carry handle as well as Mk 2 parallel type may be noticed an the later barrets. M.O.D. Pattern Room, Nottingham.


Marks 1, 2 and 3 (per 1969 pam). Mk 1 has telescoping legs, spring-ioaded so they fold at the same time. Mk 2 has fixed length legs which fold independently. Mk 3 is like Mk 1 but with non-extending legs; also may have spiked feet. In 1 947, the British Mk 3 was a Mk 2 type with independent legs; but later nominated as the type shown here.

Bren Light Machine GunBren Flash Eliminator


30-rd, Mk I. The original pattern.

30-rd, Mk I*. Auxiliary spring fitted inside the case, the front of which is recessed top and bottom to provide a seating for the spring. Converted from Mk I magazine.

30-rd, Mk )**. Similar to Mk I* but fitted with Mk I* bottom plate and bottom plate retainer. Mk I* plate has two half-moon indents. Converted from Mk I magazine.

30-rd, Mk il. Same as Mk I* magazine but new made. Slight dimensional differences.

30-rd, Mk I!*. Same as Mk I'** magazine but new made. Slight dimensional differences.

Upon the introduction of the Mk /** and Mk H* models, the Mk /, Mk I* and Mk II magazines were declared obsolescent. Some magazine cases are stamped as "III".

Mk r

Bren Machine GunBren 100 Round Drum Magazine

100-rd, Mk I. Original type. Upon introduction of Mk li drum, (a) Mk I was modified by deleting inspection cover and insertion of a washer in lieu; (b) inspection hole and slot for cover in the top cover plate deleted; (c) "WIND" and direction arrow pressed into top cover piate.to eliminate possibility of winding spring in the wrong direction.

100-rd, Mk II. Simplified design, which also incorporates the winding handle as part of the magazine, positioned alongside the loading lever.



Bren Light

30-rd Magazine Mk II*-

2. Guide, platform

5. Retainer, bottom plate,

6. Spring, auxiliary

7. Spring, platform, Mk li

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  • raimondo pirozzi
    9 years ago
  • kristian vuorela
    Are bren lowers interchangable?
    1 year ago
  • sabine
    Are bren mki and mk3 gas pistons interchangable?
    11 months ago

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