9x19mm Heavy Ball

During WWII commandos and other special forces were issued with specially silenced sub-machine guns. A number of silencer designs were tested but by 1943 the Mark IIS Sten was on issue fitted with a special barrel with a long silencer attachment. By early 1945 this had been supeseded by the Mark 6 Sten, a silenced version of the Mark 5.

All these weapons used standard British 9mm ammunition, but by 1945 the Ordnance Board had formed the view that in future a standard weapon should be used fitted with a detachable silencer. They recognised that this would probably need a reduced charge cartridge.

Trials with Patchett machine carbines fitted with a detachable silencer and using reduced charge ammunition were carried out in 1946/47. The ammunition was loaded in ROF Hirwaun 1945 cases fitted with an unringed nickel primer with a purple annulus and identified by a coloured extractor groove.

The colour codes were:

Purple extractor groove Charge weight 1.8 grains of nitrocellulose.

Red extractor groove Charge weight 3.3 grains of nitrocellulose.

Green extractor groove Charge weight 3.7 grains of nitrocellulose.

Later in 1947 a different approach was adopted; the use of heavy bullets to give a low velocity within safe chamber pressure limits. The velocity had to be below the speed of sound so was set at 900 fps. Initially .380 revolver bullets, sized to 9mm, were tried and this led to the development of a bullet weighing between 170 and 175 grains to be used with regular 9mm propellant. For bullets weighing less than 170 grains it was thought a new propellant might be needed.

Most of these early rounds were loaded into 1945 dated cases from ROF Hirwaun or Blackpole but they were actually loaded in about 1948 using primed empty cases from stock.

Between 1948 and the early 1960s various bullets were tested, including some in intermediate weights of 160 and 165 grains, these being produced by having a cavity in the base of the 170 grain bullets. A further batch of 150 grain bullets were loaded in 1971.

The 170 grain flat based bullets presented a problem as the internal walls of the 9mm case were tapered and would interfere with the base of the bullet and also reduce powder capacity. To overcome this a special case was designed where the internal walls were parallel for about 10mm down from the mouth of the case. These cases carried a special headstamp that omitted the "2Z", i.e. "RG 62 9MM (+)".

Left to right: 150 grain flat base (RG 71), 170 grain boattail, 150 grain boattail, 170 grain boattail, 170 grain boattail, 150 grain flat base (IVI),

Generally, heavy bulleted rounds were often identified by a coloured paint spot on the base of the case, whilst some had a violet bullet tip.

Known loadings of heavy bullets are:

150 grains

RG 61 9MM 2Z Boattail No coloured spot

RG 61 9MM 2Z Boattail Red spot

RG 61 9MM 2Z Flat base No coloured spot

RG 62 9MM Flat base No coloured spot

RG 62 9MM 2Z (+) Boattail Brown spot

RG 71 Flat base No coloured spot, violet tip.

160 Grains

RG 60 9MM 2Z Boattail White spot

165 grains

RG 60 9MM 2Z Boattail Grey spot

170 grains

B/|\E 45 9MM 2Z Boattail No coloured spot

RG 61 9MM 2Z Boattail Green spot

RG 61 9MM 2Z Boattail No coloured spot

RG 61 9MM 2Z (+) Boattail Green spot

RG 62 9MM 2Z (+) Boattail Green spot

RG 62 9MM Flat base No coloured spot

RG 63 9MM 2Z (+) Boattail Yellow spot, violet bullet tip

There is also a Canadian 150 grain flat base bullet with a green tip loaded into cases headstamped "IVI 69 (+)"