Mean Arms167528141
Bearing Delay 9Mm 11'' Bbl Assembled Upper Receiver$1,622.23
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Availability: In Stock
Current Stock: Out of stock
The Mean Arms Bearing Delay 9mm 4.5" upper receiver is a complete, ready-to-run 9mm AR platform system built around a proprietary ball bearing bolt carrier group that delivers the reliability and low recoil of delay-blowback operation without the complexity of traditional roller systems. Drop it onto any milspec or dedicated pistol-magazine AR-15 lower receiver—no special buffer required—and you've got a modern, tunable 9mm carbine that works with standard AR parts you likely already have.
At the heart of this upper is Mean Arms' three-ball bearing delay system, which matches the contact surface area of classic MP5 rollers but with 50% more total contact area for superior durability under modern high-pressure ammunition. Unlike fixed roller designs, the Bearing Delay system is tunable: swap the included Lifter to adjust how the bearings engage, letting you dial in performance for different ammo types, barrel lengths, or suppressor use. Two Lifters come in the box so you can experiment without buying extras.
The 4.5" barrel keeps the package compact and maneuverable while the billet aluminum upper receiver is milspec-dimensioned for drop-in compatibility. The free-float hybrid handguard (metal insert overmolded into polymer) keeps the barrel unimpeded for accuracy, while the new ambidextrous charging handle and exclusive muzzle device (complete with jam nut) round out a cohesive system. Comes with two ejectorless EndoMags so you're ready to run out of the box.
| Caliber | 9×19mm Parabellum |
| Barrel Length | 4.5" |
| Upper Receiver Weight | 2.59 lbs |
| BCG Weight | Just under 11 oz |
| Muzzle Device Thread | 1/2-28 |
| Handguard Internal Width (flat-to-flat) | ~1.375" |
| Upper Receiver Style | Slick side billet aluminum, milspec-dimensioned |
| Charging Handle | Ambidextrous, steel and aluminum |
| Included Components | Ball bearing BCG, MA upper receiver, free-float handguard, ambidextrous charging handle, muzzle device, 2 Lifters, 2 ejectorless EndoMags |
Yes. The Bearing Delay upper is compatible with both milspec AR-15 lower receivers and dedicated pistol-magazine lower receivers. If you use a pistol-magazine lower, the stationary ejector may need to be removed for full compatibility.
No. Unlike some 9mm AR builds, the Bearing Delay system works with standard, off-the-shelf AR-15 buffers.
The system is tuned by swapping the Lifter, which changes the angle of the surfaces inside the ball bearing bolt carrier group that push the bearings. This allows you to optimize performance based on ammunition type, barrel length, suppressor use, or other factors. Two Lifters are included in the box.
Each Bearing Delay upper comes complete with the ball bearing bolt carrier group, milspec billet aluminum upper receiver, free-float hybrid handguard, ambidextrous charging handle, muzzle device with jam nut, two Lifters for tuning, and two ejectorless EndoMags. (Ammunition and PMAG magazines are not included.)
SKU: 167527285 • Weight: 3oz
Availability: In Stock
Current Stock: Out of stock
The Mean Arms Bearing Delay 9mm 4.5" upper receiver is a complete, ready-to-run 9mm AR platform system built around a proprietary ball bearing bolt carrier group that delivers the reliability and low recoil of delay-blowback operation without the complexity of traditional roller systems. Drop it onto any milspec or dedicated pistol-magazine AR-15 lower receiver—no special buffer required—and you've got a modern, tunable 9mm carbine that works with standard AR parts you likely already have.
At the heart of this upper is Mean Arms' three-ball bearing delay system, which matches the contact surface area of classic MP5 rollers but with 50% more total contact area for superior durability under modern high-pressure ammunition. Unlike fixed roller designs, the Bearing Delay system is tunable: swap the included Lifter to adjust how the bearings engage, letting you dial in performance for different ammo types, barrel lengths, or suppressor use. Two Lifters come in the box so you can experiment without buying extras.
The 4.5" barrel keeps the package compact and maneuverable while the billet aluminum upper receiver is milspec-dimensioned for drop-in compatibility. The free-float hybrid handguard (metal insert overmolded into polymer) keeps the barrel unimpeded for accuracy, while the new ambidextrous charging handle and exclusive muzzle device (complete with jam nut) round out a cohesive system. Comes with two ejectorless EndoMags so you're ready to run out of the box.
| Caliber | 9×19mm Parabellum |
| Barrel Length | 4.5" |
| Upper Receiver Weight | 2.59 lbs |
| BCG Weight | Just under 11 oz |
| Muzzle Device Thread | 1/2-28 |
| Handguard Internal Width (flat-to-flat) | ~1.375" |
| Upper Receiver Style | Slick side billet aluminum, milspec-dimensioned |
| Charging Handle | Ambidextrous, steel and aluminum |
| Included Components | Ball bearing BCG, MA upper receiver, free-float handguard, ambidextrous charging handle, muzzle device, 2 Lifters, 2 ejectorless EndoMags |
Yes. The Bearing Delay upper is compatible with both milspec AR-15 lower receivers and dedicated pistol-magazine lower receivers. If you use a pistol-magazine lower, the stationary ejector may need to be removed for full compatibility.
No. Unlike some 9mm AR builds, the Bearing Delay system works with standard, off-the-shelf AR-15 buffers.
The system is tuned by swapping the Lifter, which changes the angle of the surfaces inside the ball bearing bolt carrier group that push the bearings. This allows you to optimize performance based on ammunition type, barrel length, suppressor use, or other factors. Two Lifters are included in the box.
Each Bearing Delay upper comes complete with the ball bearing bolt carrier group, milspec billet aluminum upper receiver, free-float hybrid handguard, ambidextrous charging handle, muzzle device with jam nut, two Lifters for tuning, and two ejectorless EndoMags. (Ammunition and PMAG magazines are not included.)
SKU: 167527285 • Weight: 3oz