Sanders Armory Complete AR15 AMBI Side Charging 16″ Match Grade 6.5 Grendel Type II 416R Stainless Steel Upper Assembly.
Includes a 16″ Match Grade 6.5 Grendel Type II 416R Stainless Steel Tapered HBAR Match Grade barrel with 1:7.8 Twist 5R rifling, hand-lapped, and air gauge tested.
The Sanders Armory AR15 AMBI side charging upper assembly is made of Billet Aluminum and equipped with a low-profile Steel .750 Gas Block with Nitride Finish, Stainless Steel Mid Length Gas Tube, Free Float Ultra Slim Line MLOK Handguard has a full line top rail, and 6.5 Grendel Type II (.136) Nitride AMBI BCG with Hardened Phosphate Bolt and Extractor. The upper receiver is an AR15 / M16 Mil-Spec Billet Upper Receiver; the Receiver is milled from 7075-T6 aircraft aluminum, is precision machined to mil-spec M16/M4 specifications, and features M4 feed.
- AMBI-Side Charge Upper Receiver with 7075 T6 Grade Billet Aluminum with Mil-A-8625 Type III Hard Coat Anodized Finish and M4 Feed Ramps
- 16″ Match Grade 6.5 Grendel Type II 416R Stainless Steel Tapered HBAR Barrel with 5R Rifling
- Hand Lapped and Air Gauge tested Barrel
- 1:7.8 Twist rate
- .750 Low Profile QPQ Steel Gas Block
- Mid Length Stainless Steel Gas Tube
- 13″ or 15″ Free Float Ultra Slim Line MLOK Handguard
- Tapered Fat Comp Muzzle Brake with 5/8 x 24 Thread Pitch
WHAT IS 5R RIFLING?
Retired Army man, Barrett “Boots” Obermeyer developed 5R rifling as a gunsmith in his family’s store. Boots holds a High Master Classification in both high-power rifle disciplines, is a Distinguished Rifleman, and has won numerous shooting awards at both state and national levels. The best definition of 5R rifling comes from “Boots” himself …
“5R is the form of rifling I developed for use in most target barrels, and in many sporting barrels,” he explained. “These barrels have 5 grooves, and the lands have angular sides. I have observed that bullet jackets will deform such that they remain closer to the R-form lands than they will to the sharp-edged lands present in conventional-style rifling. This reduces powder fouling at the corner of the grooves. The angled form of the lands also helps to reduce jacket failures in quick-twist barrels.”
The diagram above of rifling profiles shows the difference between traditional rifling (top) and 5R rifling (bottom). Because the edges of 5R are not square, they don’t cut into bullet jackets as much, and, with 5R rifling, the lands are opposite of grooves, while with traditional rifling, lands are opposing lands, and grooves are opposite grooves.
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