The Sanders Armory AR-15 20″ 6MM ARC Match Grade 416R Stainless Steel 1:7.8 Twist 5R Tapered HBAR COMPLETE Upper Assembly with BCG and Charging Handle. It comes with a Match Grade barrel that has been hand lapped and air gauge tested with 5R rifling. M4 Barrel extensions with a Manufacturers Limited Lifetime warranty against manufacturers defects. It is equipped with a low profile Steel .750 Gas Block with Nitride Finish and a Stainless Steel Rifle Length Gas Tube. The Free Float Ultra Slim Line MLOK Handguard has a full line top rail. The 6MM ARC (.136) Nitride BCG with Hardened Phosphate Extractor and Sanders Armory Standard Charging Handle. The upper receiver is an AR15 / M16 Mil-Spec Upper Receiver with Spring Loaded Steel Dust Cover and Forward Assist. This AR15 Upper Receiver is forged from 7075-T6 aircraft aluminum, is precision machined to mil-spec M16/M4 specifications, and features M4 feed ramps, steel dust door, and billet forward assist.
- AR-15 Mil-Spec Upper Assembly with Spring Loaded Steel Dust Cover and Forward Assist
- 20″ 6MM ARC Match Grade Stainless Steel 416R Tapered HBAR Barrel with 5R Rifling
- The barrel is Hand Lapped and Air Gauge tested
- 1:7.85 Twist rate
- .750 Low Profile QPQ Steel Gas Block
- Rifle Length Stainless Steel Gas Tube
- 15″ OR 16.25″ Free Float Ultra Slim Line MLOK Handguard
- Your choice of (5/8 x 24 Thread Pitch) Flash Hiders and Muzzle Brake
- 6MM Type 2 (.136) Nitride BCG with Hardened Phosphate Bolt and Extractor NOTE: Nitride high temperature, 975 degrees, reverses heat treating of metal’s and makes them Brittle and they will BREAK!!
- Standard Charging Handle
- The complete upper fully assembled is 5.0 LBS
What is 5R Rifling?
Retired Army man, Barrett “Boots” Obermeyer developed 5R rifling as a gunsmith in his family’s store and 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 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). Note that the edges of 5R are not square (they don’t cut into bullet jackets as much) and that with 5R, the lands are opposite of grooves while with traditional rifling, lands are opposite lands and grooves are opposite grooves.
We do not ship to the District of Columbia (Washington, D.C.); Massachusetts; Connecticut; Chicago, Cook County, Deerfield, Highland Park or Aurora Illinois; New Jersey; New York; Puerto Rico; Hawaii; or Canada. No international shipping, all must be within the 48 Contiguous United States. No APO/PPO/FPO’s.