Sanders Armory 20″ Match Grade 5.56 NATO Stainless Steel 5R Upper Assembly with AR15/M16 PREMIUM Upper Receiver with Steel Door and Forward Assist. This Premium AR15/M16 Mil Spec Upper Receiver with MPI Tested Mil Spec .223/5.56 NATO/300 Blackout Nitride BCG and Bolt with Phosphate extractor features a 20″ Match Grade 5.56 NATO 416R Stainless Steel Tapered HBAR Barrel with with 1:8 Twist and 5R Rifling. It includes a Rifle Length Stainless Steel Gas Tube, Low Profile .750 Gas Block with Nitride Finish, Standard AR15 Charging Handle, YOUR CHOICE of a Sanders Armory Slim Line, Free Float 15″ or 16.5″ MLOK Handguard, and YOUR CHOICE OF MUZZLE BRAKE between the 1/2 x 28 Stainless Steel or Nitride Tapered Fat-Comp or Flash Hider.
The Sanders Armory 18″ Match Grade 416R Stainless Steel 5R Rifling 5.56 NATO AR15 / M16 PREMIUM Upper receiver Stainless Steel Upper Assembly with BCG Package includes:
- Sanders Armory AR15 / M16 Mil Spec AR15 / M16 PREMIUM Upper Receiver
- 20″ Match Grade 5.56 NATO 416R Stainless Steel 5R Tapered HBAR Barrel with 1:8 Twist
- YOUR CHOICE OF Sanders Armory 15″ MLOK or 16.5″ KEYMOD Ultra Slim Free Float Handguard
- Low Profile .750 Gas Block with Nitride Finish
- Stainless Steel Rifle Length Gas Tube
- YOUR CHOICE OF AR-15 Stainless Steel or Nitride Flash Hider or Tapered Fat Comp
- Standard AR15 Mil Spec Charging Handle
- MPI Tested Mil Spec .223/5.56 NATO/300 Blackout Nitride BCG and Bolt with Phosphate extractor
What is 5R Rifling?
Retired Army man, Barrett “Boots” Obermeyer developed 5R rifling as a gunsmith in his families 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 jacket 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.
NO shipping to 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.