Rifle: Lee-Enfield No. 5 Mk I

Lee-Enfield No.5 MkI "Jungle Carbine"

Rifle Lee-Enfield No. 5 Mk I Manufacturer BSA and Fazakerley
Caliber .303 British Overall Length 39.5″
Action Rotation Bolt Barrel Length 20.5″
Magazine 10 rounds staggered Weight 7 lbs


The Lee-Enfield No. 5 Mk I, nicknamed the “Jungle Carbine”, is a light and handy little rifle with a kick so rough that the designers included a rubber butt pad.  Its sporty appearance meant a high demand and imposters abound.  So read the rest or beware of frauds!

British equipment in WWII was a mix of old and new, dictated by the limits of manufacturing.  The overstretched military wanted the most bang for their buck and the WWI vintage Lee-Enfields and the new, faster to manufacture No. 4 Mk I rifles were going bang just fine.  This naturally slowed any efforts to adopt a purpose built carbine for paratroops and artillery/technical units.  In the latter half of the war, with U.S. supplies and soldiers flowing into the melee and a renewed offensive the the sweltering jungles of the East they finally approached the issue.  By 1943 work was under way.

British Lee-Enfield No.5 MkI Top

The Lee-Enfield No. 5 Mk I was an adaptation of the No. 4 Mk I service rifle.  The desired changes were the reduction of length and weight.  Given the short ranged combat of the Pacific Theater the new carbine only had to match the No.4 rifle’s accuracy for at least 400 yards.  Five inches in length disappeared from the barrel and weight was removed by the addition of a more sporting-like stock and the removal of unnecessary fixtures.  The military had also toyed with lightening the No.4 rifle as it was and these efforts were applied to the No.5.  They shaved sections of unnecessary metal from the receiver and the barrel’s chamber area.  The final product was approximately five inches shorter and 1.5 lbs lighter than the No.4 rifle.

This newly lightened and shortened prototype presented problems with severe recoil and excessive light flash when firing the powerful .303 British cartridge.  These were addressed by the addition of some key features.  A conical flash hider pushed the “barrel” length a little further for a total reduction of about 4.5 inches and helped reduce the flash.  This was not intended to hide the rifleman from the enemy but rather reduce the likelihood of the bright flash from temporarily blinding the shooter.  Recoil was combated with an integral rubber butt pad at the rear of the stock, something of a military first.  Unfortunately, fears about deterioration of the rubber pushed production towards some very hard material, partially defeating the purpose of the pad.  Designers realized the rifle was so light that the sling wasn’t much of an aid in stable shooting and so redesigned the loops for carry only.  This is why the No.5 remains unique among Lee-Enfield with its side mounted sling loop.

Operation of the rifle is the standard Lee-Enfield affair familiar to anyone who has used a No. 1 Mk III* or especially the No. 4 Mk I.  The detachable magazine has a massive 10 round capacity (double most military rifles of the time) and is fed by five round stripper clips.  It’s important to remember that these magazines were not designed to be detached and reattached for loading purposes and frequent removal will eventually result in poor feeding or magazine drop.  Magazine removal was provided for ease of cleaning and repair.  When placing rounds into your stripper clip make certain to stagger the rounds as pictured for smooth feeding.

The action on the rifle is identical to the No. 4 Mk I with its cock on close, rear locking bolt.  It is extremely smooth and often praised for its ability to be cycled quickly.  Unlike the hand-fitted No.1 Mk III bolt heads, the No.4 and No.5 rifles use a set of standard sized bolt heads ranging from 0-3 with three being the longest. 00 and 4 have been observed but are extremely uncommon and may have been purpose built.  It is therefore possible to treat a No.4 or No.5 rifle with oversized headspace issue by swapping up its bolt head size, however for this reason most size 3 bolt heads are very hard to find.  Because the Lee-Enfield is a cock on close rifle you may also choose to keep it unloaded with the firing spring relaxed.  Just make absolutely certain your rifle is empty then bolt forward while holding the trigger back.  The firing pin will ease forward with the bolt and save some pressure on your spring during storage.

Lee Enfield No.5 MkI POVTwo purpose-made rear sights for the No.5 rifle were graduated up to 800 yards.  The Mk I was based on a milled leaf while the Mk II was an expedited stamped steel leaf.  The rifles are also regularly found with 1,300 yard sights made for the No.4 rifle as these are nearly identical and would function just fine.  It’s more than likely that these found their way onto the No.5 rifles as part of refurbishing but as of right now we do not have a proven explanation.  All three sights work the same.  When folded down a rear aperture known as the “battle sight” is presented for use up to 300 yards.  Beyond that range the sight must be flipped up and dialed in to the appropriate range.  This will shift the height of a slide mounted on the sight leaf.  Just use the hole in the center of this slide as your rear aperture.

The stock for the No. 5 Mk I saw only one area of significant change during production.  Some of the trials rifles were fitted with a metal cap at the front of the forestock but the manufacture time for this particular piece was extreme for its limited use and so it was omitted entirely.  Later the part returned as a stamped steel component with a slightly different angle.  Early variations are sloped at the base and uncommon.  The later stamped pieces are square.

Britain’s new carbine was officially adopted in September of 1944 but there were many widely dispersed trials rifles already in production before the acceptance date.  Originally the rifle’s design was aimed at the Pacific Theater but the main focus fell on the European theatre as a handy carbine for specialist troops such as paratroopers.  While the No.5 also made a showing in the Pacific, it was the post-WWII Malayan Emergency that seems to have really birthed the nickname “Jungle Carbine.”

Lee Enfield No.5 MkI Sides

Unfortunately the rifle was phased out pretty quickly after this point.  The British government claimed the design had an inherent flaw known as “Wandering Zero.”  It was stated that the guns could never quite be sighted in as the excessive recoil would displace the sight picture within a few dozen rounds.  I have yet to hear of or meet a collector who suffered the same problem, but we might have too much invested.  Many believe the flaw was either over played or made up in an attempt to retire the carbine early in pursuit of an automatic rifle.  If this was the case they must have failed because when the No.5 retired the No.4 continued to meet military demands into the late 50′s.

There are, however, documents tracking various tests to track down this problem.  The earliest focused on the stock and the possibility that the shortened, rapidly heating barrel was upsetting its own nest.  They later focused on yoke and extended the handguard and fore-end in an attempt to eat up some of the vibration.  These both showed limited improvement.  Efforts shifted to the lightened receiver because armorers thought it might be flexing when firing.  In some places No.4 receivers were substituted and these are reported to have been much improved.  Finally the flash hider was targeted, removed, and replaced with a weight.  These tests also showed improvement.  Ultimately, with so many potential causes, the design was scrapped entirely.

Australia, India, and Canada all took measures to create their own Lee-Enfield carbines.  Australia and India both worked on Lee-Enfield No.1 Mk III derived models because they never tooled up for No.4 production. Canada attempted to remake the No.4 much like the British.  All three abandoned their efforts in the prototype phases.  There is some evidence that Australia began actual production but they do not appear to have been issued.

The No.5 rifle is an attractive little gun and so after the war a number of fakes began appearing.  The root of the issue seems to start with the Golden State Arms Corporation who took in large numbers of No.1 and No.4 rifles starting in the 50′s.  Many of these were converted into No.5 look alikes and branded “Santa Fe Jungle Carbine” among other names.  More recently Gibbs and Navy Arms have done the same, even with Ishapore 2A1 rifles.  Furthermore, some suppliers like Numrich offer conversion kits designed to help turn a No.4 gun into a No.5 facsimile.


What should you know to spot a real No. 5 Mk I carbine?

  • No.5 rifles should be marked as such on the receiver wall.  Electropenciling is common so don’t be afraid of that.
  • No.5 rifles were made exclusively at two arsenals: BSA and Fazakerley
  • No.5 rifles don’t look like No. 1 Mk III rifles.  If it’s sort of flat and round instead of having the tall left receiver wall, just walk away.  Also note that no No.5 carbine has a tangent rear sight.  They are all aperture.
  • No.5 rifles have additional metal shaved away.  Review the following images for the differences between a No.5 and a No.4.  The carbine is always in the top half.  The shaved away metal is the gold standard for identification. Also note the image earlier in the article of the fluted shavings removed from the chamber section of the barrel.
  • No.5 rifles always have hollowed bolt handles and a fuller carved out of the visible right side lug.  No.4 rifles may or may not.
  • No.5 rifles have sights graduated to 800 yards, although they often appear with a 1,300 yard leaf like our example.

Differences between No.4 and No.5 rifles

Another common thing to watch out for when purchasing is that many sportsmen ground off the original bayonet lug on the rifle.  It should be a milled part of the flash suppressor so please make sure it’s there.  If, by reading this article, you’ve realized that you have a reproduction I’m very sorry.  Nothing beats the real thing.


14 Responses to “Rifle: Lee-Enfield No. 5 Mk I”

  1. Jeff says:

    From experience I can gladly report that the rubber butt plate does little to soften the blow of this carbine. Not sure if the rubber has just gotten harder due to its age, or if it was made hard to last longer in hot, dry conditions. But it isn’t much software than a steel plate in my opinion.

    About electro-penciling on the receiver, I don’t believe I have ever seen a stamped No.5. Also, an original bayonet will cost you as much as the rifle for one of these.

    Some 250,000 of these were made.

  2. Jeff says:

    From experience I can gladly report that the rubber butt plate does little to soften the blow of this carbine. Not sure if the rubber has just gotten harder due to its age, or if it was made hard to last longer in hot, dry conditions. But it isn’t much software than a steel plate in my opinion. nice tip on decocking the bolt while closing it. I went back and did this to mine.

    About electro-penciling on the receiver, I don’t believe I have ever seen a stamped No.5. Also, an original bayonet will cost you as much as the rifle for one of these.

    Some 250,000 of these were made.

  3. Jim says:

    Thanks for this info – I seem to have bought a “proper” Mk 5 – thanks!

  4. chris says:

    I just purchased an all numbers matching BSA Mk5 No1 1945 mfg at a local gun shop for the small sum of $100. It did not have a mag with it when I bought it so I picked one up at a gunshow along with a Santa Fe 5 rounder brought them home and took about 2 whole minuets to get them to cycle properly. I cant wait to shoot it now. I will be using it to deer hunt with. I think of all the guns I own, this is my favorite.

  5. Ken Clark says:

    I have literally looked at 100′s of web sites for a clamp and top hand guard for a 5 Mk1 with no luck. Perhaps you know where ???


    • Nagao says:

      I’m afraid your best bet for original parts are from Gunbroker or eBay. However, if you get desperate there is a conversion kit made from No.4 parts that would at least look the part. I actually did drop a real No.5 MkI in one of these years back because I was unable to find a replacement stock. Alternatively, you could grab a No.4 handguard and modify it yourself, as this is essentially what is in the kit. In either case you would have to substitute a No.4 barrel band until you could find a proper No.5.


  6. Bob Best says:

    I have had problems with case swelling and an actual case separation.
    Does tis sound like a head space problem and how can I fix or adjust it?
    I really like the little rifle, despite it’s massive “mule kick”!

    • Nagao says:

      The No.5 can be paired with No.4 bolt heads to improve headspace but I’m afraid that is the only hint I have short of going to a gunsmith. Look up the bolt head numbering conventions for the No.4 and see if you have room for a “deeper” one.

  7. Ken R says:

    I have an original Mk 5 and am trying to find a replacement leather sling as mine tore with age and died out. Any ideas?

  8. Ken R says:

    What is recommendation to keep wood stocks on Enfields clean

    • Othais says:

      On all old C&R guns you should avoid oils and cleaners if possible and stick with a moist rag and then a light coating of wax.

  9. Lance says:

    Hello, I have a correct Mk5 F, dated 10/47 that is in pristine condition. I collected Enfields for years and loved their design and history on the battlefields around the world. I gave my sons my Mk 4s but kept this Mk 5 for now as it is quite special to me . I have a problem and if anyone can help me, I would be grateful. I had a stroke some years back and some things that should be intuitive are problems now. Anyway …. I cleaned and disassembled the rifle and managed to get the bolt stuck in rearward / open position. I am embarrassed to say I cannot get it closed. What are the correct steps? Thank you! Lance

    • Othais says:

      Is there any chance you’ve let the bolt head come off the rail and not snapped it back down? Maybe it’s caught on the rear sight?

Discuss this article

× 1 = two

Share this on:
Collect likes on Facebook Tweet it or whatever Does anyone use Google+?