Site Overlay

Left Handed AR-15 Bolt Options

I’ve been researching alternative AR-15 chambering, and the differences between them all. Most folks are aware of the standard AR-15 bolt face, but may not know the actual size and what alternative cartridges will work with it.

.378″ – The Standard Bolt Face

  • .223 Remington
  • 5.56x45mm NATO
  • .300 BLK

Where can I get these bolts from?

Stag Arms – Mil-Spec shot peened Carpenter 158 steel

.420″ Bolt Face

  • 6.8 SPC
  • .224 Valkyrie

Who Makes These?

Stag Arms – Mil-Spec shot peened Carpenter 158 steel

.440″ Bolt Face

  • 6.5 Grendel – Type 2 with .136″ Head Space
  • 7.62x39mm – Type 1 with .125″ Head Space
  • 6mm ARC – Type 2 with .136″ Head Space

Who Makes these?
Maxim Firearms – 9310 Steel
Stag Arms – Material not listed
Underground Tactical – 9310 AQ Steel


.473″ Bolt Face

  • .358 SCOCOM
  • .375 SCOCOM
  • 450 Bushmaster
  • .458 SOCOM
  • .50 Beowulf

Who makes these?
Tromix – Included in Builders kit or BCG Kit