Yes sir this rifle has 5R rifling
It features five-groove (5R) rifling, which is generally thought to provide increased accuracy over older rifling types. The barrel is cold-hammer-forged 4140 chrome-moly steel with a nitride finish for corrosion resistance. For the first six inches or so it has a heavy profile, then it narrows.
The 1st AR I bought was the Ruger 556 MPR and I absolutely love it is durable l, reliable and fun to shoot. I highly recomend this rifle for home deffense or just having fun on the range

Wayne, Ruger does not list it with 5-R, which would be a big selling point, so I would confirm with Ruger Customer Service at Telephone: 336-949-5200 (Monday through Friday 8:00am - 5:00pm ET) ---- https://ruger.com/products/ar556Free/specSheets/8529.html