Andrew, this is a Threaded Barrel Model that has a 1/2 x 28 thread pitch.

yes it is threaded 1/2x28 see ****** Model Number: 26981 Caliber: 350 Legend
StockFlat Dark Earth Synthetic
FeatureStandard
SightsNone - Scope Rail Installed
Barrel Length16.38"
MaterialAlloy Steel
Capacity5
MagazineAR-Style
Twist1:16" RH
FinishMatte Black
Weight6.1 lb.
******Thread Pattern1/2"-28 x 0.4"
Overall Length36"
Length of Pull13.75"
Grooves5
Ruger Marksman Adjustable™ trigger offers a crisp release with a pull weight that is user adjustable between 3 and 5 pounds, allowing shooters to make that perfect shot.
Ergonomic, lightweight synthetic stock designed for quick, easy handling blends a classic look with modern forend contouring and grip serrations.
Soft rubber buttpad is crafted for maximum recoil reduction.
The one-piece, three-lug bolt with 70° throw provides ample scope clearance and utilizes a full diameter bolt body and dual cocking cams for smooth, easy cycling from the shoulder.
Patented Power Bedding®, integral bedding block system positively locates the receiver and free-floats the barrel for outstanding accuracy.
Factory-installed, one-piece Picatinny scope base.
Offers minute-of-angle accuracy that can make every hunt a success. https://ruger.com/products/americanRifleRanch/specSheets/26981.html