Commonwealth forces did use some systems that could be termed chest-rigs. One of the photos below shows additional ammo pouches that could be worn above the belt pouches. Certain variants of the battle jerkin used only a pair of pouches on the chest.
It is more likely that the inspiration for the Vietnam chest rig was from closer to home. There are numerous photos of Chinese soldiers in the 1920s and 30s wearing a sort of “apron” for SMG magazines.
Several types of chest rig were in use by the Viet Cong (VC) and NVA.
The “simplest” was that intended for use with the SKS. This had ten identical pockets. Each pocket could hold two 10 round chargers for the SKS, giving a capacity of up to 200 rounds. The pockets could also accommodate a 20 round M16 magazine so this rig was also used by some GIs or Vietnamese with American weapons. It is probable that some of these pouches were used for other items. They appear to be of a size that can accommodate some designs of grenade.
A variety of SMGs were in use in this conflict so there were also chest rigs designed to accommodate SMG magazines. An example is shown below:
The third type of chest rig was intended for use with the AK-47/ AKM/ Type 56 and related weapons. Typically it had three central pouches each capable of holding a pair of 30 round magazines. One or two smaller pouches were to either side. These could be used for grenades but might have held other items such as loose ammunition, field dressings, cleaning kits etc. It is worth remembering that these items were often produced at a local level or homemade so show considerable variation in both colour and details. Some items had straps that crossed at the back while others are described as having a loop that passed over the head like an apron.
One of the things to note about these items is that “chest rig” is something of a misnomer. Often you see the pouches worn quite low on the torso. A sort of “combat cumberbund”! Perhaps this transferred some of the weight to the pelvis? Rigs such as these can be worn either high or low, depending on physique, preference, type of rucksac worn etc. NVA/ VC seem to have kept their actual waist belts relatively uncluttered, often with just a grenade pouch and a canteen. Items not needed in the assault seem to have been carried in the rucksac rather than crammed into belt-mounted butt-packs or kidney pouch equivalents.
The Chicom chest rig has inspired a number of other designs. The Rhodesians often encountered enemies using this equipment and developed their own version with four or five pockets for 20 round FAL magazines.
The South Africans also adopted the chest rig. The 83 pattern shown below has a smoke grenade pouch on the wearer’s right and two smaller pouches on the left. There are small fittings that can carry a flare, pen, knife or small flashlight. A rather clever feature is that there is a map/ document pocket behind the magazine pouches. On the other hand the sides seem to have some excess material.
Some commercial imitations have possibly tried to incorporate too many “bells and whistles”. Some have ignored that a chest rig can also be a “belly rig”. Another problem is the chest rig is often seen as additional rather than alternate carrying capacity.
The Chicom chest rig is very much a compact assault order carrying ammo and grenades and little else. When you start adding pouches for waterbottles, mess tins and rain-proofs it become something else. The main improvements I would make over the original designs is provision to carry a couple of field dressings. I’d also add provision to carry a small fixed blade knife on either the left pouch or left suspender, a snaplink/ carbineer for empty magazines and a small pouch for a flashlight.
The chest region is often shadowed so a chest rig should have a light base colour to compensate for this .