The Netherlands Marines have become the first military force to adopt the 7.62x35 rifle cartridge. The Dutch are only buying 195 AR type rifles chambered for the 7.62x35. This cartridge was developed in the early 1990s so that it that could be used in M-16 (“AR”) type weapons by simply replacing the upper (the barrel and chamber) assembly of an M-4, M-16 or similar weapon. The 7.62x35 could use 5.56mm ammo magazines because the cartridge was the same size. Initially the big selling point of the (low power) 7.62x35 cartridge was that it was subsonic and thus an ideal sniper cartridge (using a silencer) for ranges up to about a hundred meters. But others saw opportunities for a supersonic version.
In 2009 U.S. SOCOM (Special Operations Command) had a high velocity version (7.62x35 with more propellant) developed. Now you had a cartridge similar in size to the 7.62x39 Russian AK-47 round but with more hitting power and better accuracy at longer (several hundred meters) ranges. SOCOM operators are believed to have used 7.62x35 equipped M-4s in combat and were apparently satisfied with its performance but SOCOM has not yet adopted the round on a large scale but both subsonic and supersonic versions are available to any operators who feel they need it.
Police forces have been heavy users of the 7.62x35 because in urban situations it limits the risk of a sniper or SWAT officer with an M-4 firing at someone and having some of those shots go through walls or long distances to his innocent civilians. The 7.62x35 is also used in a wide variety of weapons that normally fire the 5.56mm round. For example, the Dutch marines normally use the HK416, a weapon first adopted by SOCOM in 2004. The HK416 uses the uses a short-stroke piston system and 5.56mm ammo, so it can quickly be converted to use 7.62x35 by replacing the barrel assembly.