Please note that these bolts ARE NOT compatible with standard M4 barrel extensions.

Centurion Arms' new bolt design will make your AR platform more reliable and last longer with a lifetime guarantee against bolt breakage. Their new bolt has a body profile that creates a larger radius between the bolt lugs and the body that allows the pressure to be spread over a larger area reducing stress points which leads to lug failures. They have also added dual ejectors that help rotate the brass off the bolt face faster to ensures more reliable ejection in rifles while running suppressed or going back and forth between suppressed/unsuppressed. This also helps with platforms that are considered to be “over-gassed”. E4 bolts include a taper lug design creating more strength.

E4 Bolts will require the “T” marked barrel extensions or the Knights Armament E3 extensions to accommodate the taper lug design.

E4 bolts use standard gas rings for logistical commonality and also use standard extractors with black inserts and either Colt OEM extractor springs or Centurion Arms' upgraded 5 coil chrome silica stress relieved spring for ultimate reliability.

Lastly, the E4 bolts do not require a proprietary cam pin or firing pin as they are designed to support standard pins.  However, they are NOT compatible with KAC's proprietary E3 firing pins or cam pins.

Currently Compatible T-Marked Centurion Arms Barrels*:

• 2024 Batch of 14.5" Hammer Forged Carbine Socom Barrels
• 2024 Batch of 11.5" Hammer Forged Carbine FBI Barrels
• 2024 Batch of  8.5"  Hammer Forged BLK300 Barrels 
• 2024 Batch of  16"   Hammer Forged Midweight Midlength Barrels

*Previously purchased barrels from earlier batches will NOT have taper lug extensions. You must check your barrel prior to use with E4/ETB bolts.