Mark 8Z Ball .303 Machinegun Magnum
By David M. Fortier
In the darkness of 23 August 1916 a battalion of British infantry worked feverishly bringing cases of ammunition and water forward. They were tasked with bringing up enough supplies to keep 100 Coy, Machine Gun Corps well supplied. It was no light work as the ten guns in question were Vickers .303 medium machineguns. When the signal to fire was given on 24 August the ten Vickers fired for 12 hours non- stop. The only pause was to change ammunition belts and barrels. Between ten guns they fired just shy of 1 million rounds. One gun actually averaged 10,000 rounds an hour for 12 hours. They used 100 barrels and an untold amount of water was turned to steam in the process. In the end their assigned task was accomplished. They had been charged with denying the “Hun” movement over a far distant hill. For 12 hours they had made the hill impassable. No reinforcements got through, no ammunition, food or water was brought forward, communication was effectively cut. In both World Wars and afterwards the Vickers Mk I machinegun proved eminently capable of providing long range indirect fire. It was used to such an extent in this manner that a special load was developed for use solely with the Vickers, the .303 Mk 8Z.
Unlike its contemporaries the .303 British was originally a blackpowder cartridge when it was first adopted on 2 February 1889. The .303 Mk I Ball load consisted of a 215 grain round nose bullet on top of 75.5 grains of blackpowder. It was soon changed to cordite and remained basically the same up through the Mk VI ball loading. This drove a 215 grain round nose at 2060 fps. The charge was 30-32.5 grains of cordite.
The big change came with the adoption of the famous Mk VII ball round. This load consisted of a 174 grain flat based spitzer on top of 37 grains of modified cordite. Velocity was 2440 fps. This load was in service at the outbreak of World War I and continues to give outstanding service in various places around the world today. For extreme long range use of the Mk VII ball did have two drawbacks. One was the velocity, the other was the flat base projectile design. Both were easily remedied.
Before delving deeper it is first important to understand British thinking as far as projectile design was concerned. They did not deny the long range superiority of the boattail (they referred to it as streamlined) projectile over the flat base. They readily admitted a boattail projectile has a greater capacity for overcoming air resistance, flatter trajectory, higher striking power at longer ranges, and greatly increased ranging power. However they also felt that it was far easier to manufacture a square (or flat) base projectile and therefore it was easier to maintain the standards of manufacture. This in turn would produce a more consistent and accurate projectile. Poorly manufactured projectiles may give rise to oscillation (wobble) in flight producing dismal accuracy at anything but short range. They felt that since mass production is at its peak during wartime that it was likely that boattailed bullets manufactured under such conditions might lack the careful finish needed to guarantee accuracy. The Germans however embraced boattail projectiles and it is interesting to note that in his book ‘With British Snipers To the Reich” Captain Shore mentions coming across specimens of German projectiles whose tapered bases were definitely lacking symmetry.
If you scratch your head at their (British military) thinking, just remember that when British tankers complained that the hammer spur on their revolvers were catching on this or that as they clambered in and out of their vehicles they came up with a surefire fix. Instead of simply issuing flap holsters they removed the hammer spurs and made all their service revolvers double action only.
Flat base or not the Mk VII ball round proved to be an excellent rifle cartridge. To make it more efficient for long range indirect fire they upped the velocity from 2440 fps to 2550 fps. Then they added a 174 grain projectile with a long boattail. This was loaded atop a charge of 37 grains of nitro-cellulose propellant as opposed to the normal cordite loading. So the Mk 8Z ball, for machineguns only, was born. This load gave the Vickers machinegun a maximum range of 4500 yards (4.1 km)! This is in comparison to the Mk VII’s maximum range of 3700 yards (3.38 km). Terminal velocity of a dropping .303 Mk VII at this range is only 315 fps which equates to about 40 foot-pounds of energy.
You can easily tell Mk VII ball from Mk 8Z ball by simply looking at the head stamp. The British military headstamp gives the manufacturer’s name abbreviated to one or two letters. “RG” for example indicates the round was manufactured by the Royal Ordnance Factory, Radway Green in Cheshire, ‘K’ indicates manufacture by Kynoch and so forth. The year of assembly is given, and the cartridge type. Up until the end of 1944 Roman numerals were used to indicate the mark type of the cartridges. VII or 7 would indicate the standard Mk VII cordite loaded ball. A suffix of ‘Z’, such as ‘7Z’ would indicate nitro-cellulose propellant instead of cordite. So a round with a head stamp of K63 8Z would be a Mk 8Z ball round loaded with nitro-cellulose by Kynoch in 1963.
A letter prefix on the mark designation before 1957 identified projectile type. No prefix indicated ball. The codes are listed below:
B-Incendiary
O-Observing
D-Drill
P-Practice
E-Smoke Bomb Projector
Q-Proof
F-Semi-Armour Piercing
R-Explosive
G-Tracer
U-Dummy
H-Grenade Discharger
W-Armour-piecing
L-Blank
Where a cartridge performed two functions the prefix could use 2 letters, such as ‘PG’ for Practice Tracer. So a designation of G8Z would indicate Mark 8 Tracer, loaded with Nitro-cellulose. Until the adoption of the NATO color code in 1957 the British used a color code as follows:
Of special note is British wartime experience with the barrel erosion characteristics of Mk VII ball (cordite) and Mk 7Z and 8Z (Nitro-cellulose). They found that barrels should be used with either cordite ammunition (Mk VII) or Nitro-cellulose ammunition (Mk 7Z and 8Z) but not with both. This was due to the different wear patterns of the two different propellants. They stated this was especially important for overhead fire. I’d hate to know who found that out!
I took examples of different types of .303 ball cartridges, pulled the projectiles and weighed the components. For Mk VII ball, I had examples from 1949 vintage Radway Green and 1948 vintage Greenwood and Batley. For Mk 8Z I had examples made by Kynoch in 1963. And to make things interesting I used some Greek ball manufactured by Greek Powder and Cartridge Co., in Athens and Sellier and Bellot in Vlasim, Czechoslovakia (I have been extremely impressed with Sellier and Bellot .303 Ball, it’s really good stuff). Data is contained in the chart. I then trundled all my gear out to my car and drove to The Outdoor Sportsman in Northport, Maine. The range is class 3 friendly and the owner Carl Kosomo helped with the testing. To check for accuracy I used a custom No. 4 Enfield Tactical rifle with 26” heavy fluted Douglas match barrel, synthetic stock, and 3X9 Leupold.
I was pleased as the Mk 8Z shot into an inch at 100 yards. Not bad for machinegun ammunition. Average velocity was 2559 fps and recoil seemed no different from Mk VII ball, fairly mild. Point of impact was 1.5 inches higher than for MkVII ball. Bolt opening was normal and cases extracted easily. Primers were normal with no signs of higher than ordinary pressure.
While I did not have the opportunity to perform any long range tests, it has been my experience that the .303 Mk VII gives easy hits out to 850 yards or so (with a good rifle). Somewhere around 950 to 1000 yards though, for direct rifle fire the old girl runs a little short on steam. It would be interesting to see how much of an improvement the Mk 8Z offered. It doesn’t seem to be very different from some of the new 175 grain 7.62 NATO match loads that are now coming into vogue. In all truthfulness, the Mk 8Z probably doesn’t offer much of an improvement over the Mk VII for rifle use at typical infantry engagement ranges. For it’s intended purpose though I’m sure it was extremely effective. There is no doubt that a number of Vickers firing Mk 8Z ball could wreak havoc at incredible distances. One does not normally worry about rifle caliber machinegun fire at a distance of 4 kilometers. In this case it would be a mistake you wouldn’t make twice.
The Vickers Mk I machinegun passed into oblivion in 1968, and with it the Mk 8Z ball round. Their indirect fire role having been usurped by the 81 mm mortar. With its passing a chapter in machinegun history closed. It has been said that once one has tap traversed on the Vickers the fascination of the weapon remains for all time. The Vickers gun will stand for all time as a truly great machinegun. So the .303 British will stand as a truly great military cartridge.
This article first appeared in Small Arms Review V2N11 (August 1999) |
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