In the late 1980s, FN tried to develop a replacement for the venerable Browning M2. They also tried to develop this weapon to match the power effects of the Soviet KPV machine gun, which is chambered for 14.5×114 mm. This round is a tremendously powerful heavy machine gun round, able to penetrate 10 mm of steel armor, angled at 30 degrees at a distance of 1,350 m.
This took quite a bit of effort. Originally FN tried necking the Hispano-Suiza 20 mm round down to 15 mm, but this tore up the barrels too quickly. They eventually settled on 15.5×115 mm rounds with a driving band, much like a very small artillery shell. Also interestingly, they used a necked-out KPV case as the base for their new cartridge. This protracted development cycle did nothing to help the cost of FN’s new weapon.
The BRG-15 itself possesses some curious design elements. It is a dual-feed weapon, feeding from both sides simultaneously. Spent cases are ejected out the bottom. The BRG-15 also possessed a quick-change barrel system. It was 2.15 m (just over seven feet) long overall, and weighed 60 kg (just over 132 lbs) without a tripod, of course. Contrast this with an overall length of 1.65 m (5.4 ft) and a weight without tripod of 38 kg (83.78 lbs) for the Browning M2.
The BRG-15 was cancelled in the early 90s when a lack of buyers and troublesome finances at FN forced them to be selective about their projects. They chose to focus on development of the P90 instead.
This is a case where I actually agree with the termination decision. Clearly, the KPV provides similar, though somewhat inferior, ballistic performance. The KPV was also designed in 1947, so it’s going to be much cheaper to acquire either directly from the Russians or on the secondary market.
Further, in the current age, I do not see the value of such a weapon. The Browning M2 is not a perfect weapon, but it and its ammo are firmly established in our arsenal. The BRG-15 adds considerable weight and bulk in both weapon and ammunition for vehicle mounts or manpack loads. While it is able to perforate most classic APCs, more modern vehicles have the edge in protection. 15.5 mm is also too small to provide a useful explosive payload. The larger 20 mm is a marginal, obsolescent autocannon caliber for vehicles, both in terms of armor penetration and explosive payload. 25 mm is increasingly being seen in a similar light.
At present, the heavy machine gun is a secondary weapon. A weapon to supplement the primary armament of vehicles, or to provide armament to otherwise unarmed light vehicles. Here the lighter, lower cost weapon holds the advantage, even if it is less effective overall at penetrating armor. There are few enough targets that the BRG-15 can defeat but the Browning M2 cannot that it is not worth deploying the heavier BRG-15.
Here, I find myself in agreement with the Russians once again. Having developed the KPV in the late forties, and hence having a cheap, established weapon in the same size and performance class as the BRG-15, they have chosen instead to focus and primarily field weapons that fire the 12.7×108 mm round. In other words, they have opted for weapons in the same performance class as the Browning M2 when cost is much less of an issue.
Verdict: Funding Request Denied by the Borgundy War Department Army Ordnance Board