Key Question: Can this design deliver?
One of the greatest revolutions in military small arms occurred during WWII. The German MG34 and MG42 almost totally revolutionized light machine guns. Prior to the war, most nations fielded light, magazine-fed machine guns as the light machine guns in a weapons platoon or section. After the war, almost everyone wanted a light belt fed for that role.
The Soviets developed the RPD, the Americans slowly developed the M60, but most of the world adopted the FN MAG. The Germans, Italians, and some other nations simply adapted the MG42 to new postwar calibers, creating various rechambered variants: MG1, MG2, MG3, and MG 74.
However, the Swiss Schweizerische Industrie Gesellschaft (SIG) was not about to let this opportunity pass them by. Like their neighbors, postwar Switzerland was also refreshing their small arms arsenals in the 1950s. A new pistol, machine gun, and rifle were needed. SIG submitted designs for all three contracts, but it only won the rifle and pistol contracts with the P210 pistol and Stgw 57 assault rifle.
For the machine gun contract, SIG’s MG50, a gas operated weapon competed with Waffenfabrik Bern’s MG51, a highly refined version of the MG42. The MG51 won the trials, and the SIG machine gun was relegated to obscurity. An attempt was made in 1953 to submit it to Swedish trials as the MG53, but it went nowhere.
But SIG wasn’t done with machine guns. Following the success of their Stgw 57 assault rifle, they adapted the roller-delayed blowback mechanism to a new machine gun, the SIG MG55. In doing so, they would create the first successful roller-delayed blowback machine gun, a few years before H&K would make the HK21. The first variant was submitted again to Swedish trials as the MG55-1 in 6.5mm Swedish, but it too would not win. Sweden eventually accepted a variant of the FN MAG in 7.62x51mm NATO as the Ksp 58 as their standard machine gun.
SIG then redid their naming system for machine guns, and the MG55 became the MG 710. A variant in 8mm IS (MG 710-2) was produced, but the only successful variant would be the MG 710-3 in 7.62x51mm. The SIG MG 710-3 would be sold to a few small African, South American, and European militaries, it would not enter Swiss service.
By most accounts, the SIG MG 710-3 was successful in its role, due to the general reliability of roller-delayed blowback actions in adverse conditions. Unlike the FN MAG, it requires no adjustment to gas to function reliably. It’s notable as being one of the lightest full caliber machine guns of its era, weighing in at only 9.25 kilograms to the FN MAG and MG3’s 11 kilograms. Only the Soviets would later produce a gun in a similar weight bracket with the PKM, which comes in at around 9 kilograms.
So is there a future for the MG 710-3 or designs similar to it? Probably not. Gas operation, in both the PKM and FN MAG and its derivatives, has proven to be the dominant operating system for machine guns due to its relative simplicity and cheapness of production. Roller-delayed blowback, whether in the SIG or H&K systems requires a lot of money and time to machine the precisely fitted bolts and bolt carriers in which the rollers work. Like the SIG 710-3, H&K’s own roller-delayed blowback machine gun, the HK21 only saw limited adoption, though it did serve in an extremely limited capacity in the Bundeswehr as the G8.
Also, it’s unlikely that the two companies that carry on SIG’s legacy hold any of the expertise developed on the MG50 and 710. Sig Sauer, Inc and Sig Sauer, GmbH have shown very little interest in reviving legacy products of the Swiss SIG, apart from a limited run of the Sig 556 rifle. Bringing back an old roller-delayed machine gun would not fit into their product line, and Sig Sauer, Inc is currently producing their own gas-operated machine gun, which appears to be a clean slate design with a similar layout to an FN MAG.