Rock River Arms126513769
RRA Complete Mid-Length A4 Upper Receiver 450BM 16" Barrel with 5-Round Magazine$758.93
Availability: In Stock
The Rock River Arms A4 carbine upper in .350 Legend is a complete, ready-to-run upper receiver built for hunters and shooters who want modern performance in an efficient mid-range caliber. This 16" barrel upper drops straight onto your AR-15 lower—no gunsmithing required—and comes fully assembled with bolt carrier group, charging handle, and a 10-round magazine, so you can head to the range or field without hunting down parts. The .350 Legend has carved out a genuine niche for hunters: it's legal in many states where other rifle rounds aren't, ballistically capable for medium game and target work, and soft enough to shoot comfortably all day.
RRA engineered this upper with practical features that reflect real-world use. The chrome moly barrel is 1:16 twist—the standard for reliable .350 Legend performance—and chambers true. The 13" M-Lok free float rail keeps the barrel isolated from the handguard for consistent accuracy, and its extended length gives you solid hand placement and room for modern accessories. Up front, a low-profile gas block feeds a carbine-length gas system, and the RRA Operator Brake (1/2-36 threaded) tames recoil and helps with muzzle control. Every component is factory-installed and tested.
Whether you're building a ranch rifle, a hunting carbine, or a short-range target gun, this upper handles the job without complexity or compromise. If you're new to the .350 Legend or just want a turnkey upper that works, RRA's attention to detail shows in the execution.
| Caliber | .350 Legend |
| Barrel Length | 16 inches |
| Barrel Material | Chrome moly |
| Barrel Twist | 1:16 |
| Handguard | RRA 13" M-Lok free float rail |
| Gas System | Carbine length |
| Gas Block | Low profile |
| Muzzle Device | RRA Operator Brake, 1/2-36 thread |
| Bolt Carrier Group | Included |
| Charging Handle | Included |
| Magazine | 1 × 10-round capacity |
| Configuration | Complete upper receiver (requires AR-15 lower) |
This is a complete upper receiver designed to mate with any standard AR-15 lower receiver. You'll need a compatible lower to have a functioning rifle; the upper alone cannot be fired as a standalone unit.
Yes. The .350 Legend was designed specifically for hunting and is legal in many states where traditional rifle calibers are restricted. The 16" barrel and carbine-length gas system make it handy for field use, and the free float rail supports consistent accuracy. Always check local regulations for your specific area and game.
The upper assembly is complete and ready to install: it includes the barrel, handguard, bolt carrier group, charging handle, and one 10-round magazine. You do not receive a lower receiver or sights.
The upper includes a 13" M-Lok free float handguard with M-Lok slots for mounting lights, bipods, grips, and other tactical accessories. The upper itself features a flat-top Picatinny receiver with standard AR-15 mounting locations for optics and sights.
SKU: 126513816 • Width: 6in • Height: 5.5in • Depth: 32in • Weight: 6.31oz
Availability: In Stock
The Rock River Arms A4 carbine upper in .350 Legend is a complete, ready-to-run upper receiver built for hunters and shooters who want modern performance in an efficient mid-range caliber. This 16" barrel upper drops straight onto your AR-15 lower—no gunsmithing required—and comes fully assembled with bolt carrier group, charging handle, and a 10-round magazine, so you can head to the range or field without hunting down parts. The .350 Legend has carved out a genuine niche for hunters: it's legal in many states where other rifle rounds aren't, ballistically capable for medium game and target work, and soft enough to shoot comfortably all day.
RRA engineered this upper with practical features that reflect real-world use. The chrome moly barrel is 1:16 twist—the standard for reliable .350 Legend performance—and chambers true. The 13" M-Lok free float rail keeps the barrel isolated from the handguard for consistent accuracy, and its extended length gives you solid hand placement and room for modern accessories. Up front, a low-profile gas block feeds a carbine-length gas system, and the RRA Operator Brake (1/2-36 threaded) tames recoil and helps with muzzle control. Every component is factory-installed and tested.
Whether you're building a ranch rifle, a hunting carbine, or a short-range target gun, this upper handles the job without complexity or compromise. If you're new to the .350 Legend or just want a turnkey upper that works, RRA's attention to detail shows in the execution.
| Caliber | .350 Legend |
| Barrel Length | 16 inches |
| Barrel Material | Chrome moly |
| Barrel Twist | 1:16 |
| Handguard | RRA 13" M-Lok free float rail |
| Gas System | Carbine length |
| Gas Block | Low profile |
| Muzzle Device | RRA Operator Brake, 1/2-36 thread |
| Bolt Carrier Group | Included |
| Charging Handle | Included |
| Magazine | 1 × 10-round capacity |
| Configuration | Complete upper receiver (requires AR-15 lower) |
This is a complete upper receiver designed to mate with any standard AR-15 lower receiver. You'll need a compatible lower to have a functioning rifle; the upper alone cannot be fired as a standalone unit.
Yes. The .350 Legend was designed specifically for hunting and is legal in many states where traditional rifle calibers are restricted. The 16" barrel and carbine-length gas system make it handy for field use, and the free float rail supports consistent accuracy. Always check local regulations for your specific area and game.
The upper assembly is complete and ready to install: it includes the barrel, handguard, bolt carrier group, charging handle, and one 10-round magazine. You do not receive a lower receiver or sights.
The upper includes a 13" M-Lok free float handguard with M-Lok slots for mounting lights, bipods, grips, and other tactical accessories. The upper itself features a flat-top Picatinny receiver with standard AR-15 mounting locations for optics and sights.
SKU: 126513816 • Width: 6in • Height: 5.5in • Depth: 32in • Weight: 6.31oz