Ammo for Lee Enfields

[Bruce_in_Oz]

Taken from
"Regulations For Army Ordnance Services - Small Arms Ammunition"
Dated 24th February 1945


Rifles *
Mk8Z SAA (Small arms ammunition) will not be used except as in the case of the Bren gun if necessity should arise.

* Although the use of Mk7 and kindred types of cordite loaded, flat base bulleted ammunition reduces Mk8Z barrel life, the reverse is not the case. No deleterious effects will therefore be produced by the occasional and restricted use of Mk8Z ammunition in these weapons.

Its interesting to note that any machine gun barrel that had fired Mk7 ammunition had to be stamped with a 7 and returned to stores and a Mk8Z barrel 'demanded' in exchange.
Mk7 ammunition wears out Mk8Z barrels !!!

As a side issue the booklet makes note that US manufactured 303 ammunition differs from UK manufactured ammunition - I didnt know that.

That all makes sense. Mk8Z was loaded with a granular nitro-cellulose propellant that generated lower temperatures. The Mk7, being stoked with good old cordite, ran at significantly higher temperatures and thus was responsible for a greater rate of erosion at the throat.

If you have a "pre-loved" Lee-Enfield that has fired a lot of Mk7, it will have throat erosion. Feeding it Mk8Z will ruin it quite quickly as the base of the bullet does not fully expand and thus gas blow-by will eat away at the already eroded section. "Sporting" solid based boat-tails are as bad, if not worse.

I suspect the issue of restricting the use of Mk7 ammo because it "wears out" Mk8 rated barrels, is related to the heat issue as per above. The higher operating temperature of Mk7 means that in machine guns, destructive heat buildup is much quicker. This is slightly more of a problem in air-cooled guns like the Bren, than in water cooled classics like the Vickers.

[Thunderbox]

That all makes sense. Mk8Z was loaded with a granular nitro-cellulose propellant that generated lower temperatures. The Mk7, being stoked with good old cordite, ran at significantly higher temperatures and thus was responsible for a greater rate of erosion at the throat.

If you have a "pre-loved" Lee-Enfield that has fired a lot of Mk7, it will have throat erosion. Feeding it Mk8Z will ruin it quite quickly as the base of the bullet does not fully expand and thus gas blow-by will eat away at the already eroded section. "Sporting" solid based boat-tails are as bad, if not worse.

I suspect the issue of restricting the use of Mk7 ammo because it "wears out" Mk8 rated barrels, is related to the heat issue as per above. The higher operating temperature of Mk7 means that in machine guns, destructive heat buildup is much quicker. This is slightly more of a problem in air-cooled guns like the Bren, than in water cooled classics like the Vickers.

I think thats in danger of over-simplifying it. Its not really a factor of the heat build-up nitro cf cordite. Erosion and temperature rates between cordite and nitro are negligible - there is just a slightly different barrel wear pattern resulting. Most technical sources actually quote a longer service barrel life for cordite over nitro.

The regulations about ammo in machine guns have a lot to do with guaranteeing the safety of "overhead fire". A machinegun by design produces a "cone" of fire in any case - ie a much larger group than the equivalent rifle - and so the lower edge of this trajectory envelope is critical when the gun is set to fire over own troops. Hence its more to do with the poor set-up of boat-tail bullets in "cordite bores"and the resulting ballistic variations, rather than accelerated wear from cordite.

[Mk VII]

My uncles (father's side) traveled to New England around 1940 in order to work in the Winchester plant which was apparently churning out huge quantities of 303 ammo for shipment overseas. It was loaded w/ a powder that looks like an IMR type. Headstamped WRA w/ the year of mfg.

Winchester (and Remington) were approached in March 1940. Neither was keen to negotiate. Winchester, in particular, had had a bad experience with British contracts in the last war, on which they had ended up losing money. They demanded payment of the entire cost of new plant and 100% down-payment on the order, and were not keen to bid even then.

[Beerhunter]

This is slightly more of a problem in air-cooled guns like the Bren, than in water cooled classics like the Vickers.

Remember though, Mk8z was for the Vickers not the Bren. The Bren was fed by the members of the Infantry Section from their bandoleers of Mark Seven. Source: Infantry Training, The Light Machine Gun & Section Handling.

[Alan de Enfield]

From : "Small Arms Ammunition" (again)

"One of the advantages of Mark8Z ammunition is that the barrel maintains accuracy and elevation until the actual moment of collapse. No indication of approaching barrel failure is given when Mark8Z ammunition is used. Accuracy is liable to breakdown very suddenly, and the barrel becomes dangerous for use for overhead fire in the latter stages of its life. To ensure the safety of our own troops during overhead fire by medium machine guns, the life of a .303-inch Vickers gun barrel using Mk8Z ONLY, has therefore been fixed at 10,000 rounds ( or 40 belts). This figure is well within the number of rounds successfully completed by the earliest barrels firing and endurance and accuracy test under conditions of excessively rapid rates of fire. If, however, even a few rounds of cordite loaded SAA (small arms ammunition) are fired the Mk8Z accuracy life drops considerably".

It goes on to say that whilst the Bren uses Mk7 the Mk8Z produces less muzzle flash & it may be desired to use Mk8Z for 'special purposes' ie night patrol.

[Edward Horton]

The original poster asked the question is modern commercially made .303 ammunition safe to shoot in his No.4 Enfield rifle.

The original smokeless powder loading for the Enfield rifle was 17 tsi which was upped to 18 tsi and then finally 19 tsi. The problem with the British (tsi) conversion to PSI is the method and placement of the copper crusher pellet in pressure testing. The British placed the copper crusher pellet at the very rear of the case where the bolt face would be, we the Americans and SAAMI place the copper crusher pellet midway along the case length and this is more properly called axial and radial pressure testing.

All figures in British long tons.

Amount : 17 tons per sq. inch (tsi)
Equals : 38,080 pounds per sq. inch (CUP) copper units pressure

Amount : 18 tons per sq. inch (tsi)
Equals : 40,320 pounds per sq. inch (CUP) copper units pressure

Amount : 19 tons per sq. inch (tsi)
Equals : 42,560 pounds per sq. inch (CUP)

It is my understanding that commercial American ammunition manufactures keep the chamber pressure of the .303 British below 43, 000 CUP in deference to the older Enfield Rifles still being shot today.

American .303 British maximum chamber pressures are 46,000 CUP or 49,000 PSI transducer method.

I'm not sure where the missing 3,000 CUP pressure went between the British axial method and the American radial method of chamber pressure readings, but I can tell you American SAAMI commercial ammunition is safe to shoot and has a lower chamber pressure than military ammunition and it also doesn't go click poof......................... bang.


I also don't care what Mk. 303 ammo you use, NONE of you are going to shoot over MY head with a new or used .303 barrel.

[Bindi2]

I am not that bad a shot Ed. Would use a sniper not the minute of man rifle to give you better than 50% chance

[Peter Laidler]

On the subject of overhgead fire Ed, in the mid 60's...'66ish, we had 6 or so Vickers guns that were kept calibrated solely for this purpose, to fire over the heads of troops training in an area known as Battlesbury Bowl. When the GPMG/L7 FN MAG had been given the all clear to replace the big Vickers, there was some doubt about the fastness of the GPMG buffered tripod to ensure the guns safety in the OHF role. So, in their wisdom, and you're not going to believe this....., a 6 wheel saracen troop-carrier was up-armoured, armoured glass drivers/commanders/observers slits etc and painted yellow with black stripes, and driven into the training area called 'the bowl' while the 6 GPMG's were hosing down the opposite hillside. The driver and commander then reported on the radios when the first bullets started pinging off the hapless Saracen. From that, they formulated the degree of wear that was permissable on the buffered tripods and GPMG barrels. Occasionally the aerials got shot off so radio contact was lost but................. I sat inside as a spotter on many occasions and when the bullets hit it, it was like sitting inside an oil drum when someone was throwing apples at it...., you certainly knew you were in the fire-ground

It's actually TRUE. The trial took place over many weeks/months but the outcome was that the last function of the Vickers could be achieved by the GPMG....except in the Radfan mountains and Aden and along the hill forts of Malaya and Borneo but that's another story.

Afterwards the shot-up and virtually destroyed Saracen was left on the ranges as a hard target. As you can imagine, this now up-armoured leviathan proved impossible to destroy using the anti-tank weaponry of the day, the old 3.5" M20 rocket launcher and the Carl Gustav 84mm anti-tank gun

[neal455]

I wonder if the guys sat in the Saracen ever wondered about the health and safety implications ? Probably way to busy filling in the cosh forms to notice the rounds hitting . . . .

[spinecracker]

On the subject of .303 surplus ammunition, I have stumbled across a wooden case of ammunition marked "288 CART .303 BALL Mk7 CTN", "I.S.A.&A." and "RG19.1.53A" on the outside, and the sealed metal box inside has "H 52 Mk.1. HB & S 1945". On the underside of the wooden lid is stamped "SV59SA". I think I can safely assume that the contents is corrosive as heck, but would the contents be in stripper clips and bandoleers or in boxes? What might be the country of origin? I obviously do not want to open up the sealed portion until I have to - especially if I sell it, then that metal lid is staying on!