Multi-Radial Rifling (MRR) is a special rifling type, which unlike conventional rifling doesn’t have sharp edges. This rifling is described as being made of two different alternating radiuses. Although it is not the polygonal rifling (most notably seen in Glock pistols), it is still very similar in appearance and performance.
The multi-radial rifling is pioneered by Sabatti several years ago. So it is a relatively new concept, but it seems to be gaining popularity. Sabatti offers more and more rifles with such a rifling pattern. According to Sabatti, the new rifling has a number of advantages compared to traditional ones. It results in less bore fouling and allows easier cleaning of the bore.
Unlike conventional rifling, MRR doesn’t form the distinct grooves on the bullet jacket, but rather squeezes the bullet to fill the bore geometry. The result is a better bore seal with less gas escaping past the bullet. The latter allows having around 12% more muzzle velocity. The MRR also has a better design of throat portion, where the bullet transitions into engaging the riflings. So with more velocity, less bullet deformation, and better throat geometry, the precision of the rifle also increases.
Sabatti’s MRR rifling also forms well during the cold hammer forging barrel manufacturing process.
There is another interesting statement by the manufacturer, which I’ll quote:
Shooters can improve Multi-Radial barrel performance by simply lapping the bores with abrasive paste pads with no fear of ruining the rifling edges like with traditional rifling.
Here is also a video telling about the MRR:
All the features described in the article are claimed by Sabatti and if they are correct, then this technology can be a real improvement in rifling design.
Sabatti firearms are introduced in the USA by the Italian Firearms Group.