The Trajectory Arms VMU (Variable-Mitigating Upper), as its name suggests, mitigates variables that may affect reliability and accuracy. We go to great lengths to make each upper as consistent as possible and remove the pain points that may cause you issues down the road.
Along with a set of excellent components, when it comes to actually building these, there is a lot wrapped into them that isn’t immediately visible.
- Receivers are trued on a lathe to ensure they are square, not just lapped with a “truing bar” and a hand drill.
- Barrel is bedded into the receiver to provide a snug fitment and improve accuracy.
- Barrels are inspected and hand picked from a larger batch. An inspection sheet is included just like what is provided with our normal barrel services.
- Gas block is pinned with a heavy duty stainless steel coil pin which balances strength, corrosion protection, and end user serviceability.
- Feed ramps are hand polished to remove machining marks, improve on the violent feeding process, and reduce the amount of foreign material build up in the receiver.
- Bolt is headspaced and matched to the barrel to provide more accuracy and longer lifespan.
- Gas system features tighter fitting parts, including our highly respected gas tubes for efficient gas delivery to the BCG.
- The BCG is hand picked for tighter tolerances, optimal firing pin protrusion, and is full-auto test fired on its own to verify functionality.
- 7075 SLR HDX rail was chosen to provide extra rigidity and reduce rail flex.
- Forward Controls Design 6315 Muzzle device provides excellent flash suppression and serves as a moderate compensator due to the modified ports. Can be upgraded to the key-mount version if you intend to use a suppressor.
- Full-auto test fired as an assembly with no less than 50 rounds to ensure functionality and to start the break-in process.
Full parts list:
- Rosco Bloodline 12.5″ 5.56 Barrel with conservative .0685″ gas port for excellent performance suppressed or unsuppressed.
- BRT M4 Forged upper receiver
- BRT BCG with Sprinco ejector/ejector spring upgrade, dimpled cam pin, and full auto test fired. Hand picked for tighter tolerances.
- SLR HDX 7075 aluminum rail
- SLR GB7 low profile gas block
- Trajectory Arms black nitride gas tube
- Forward Controls Design 6315 flash hider
- Trajectory Arms USGI charging handle made from forged 7075 aluminum
- Further configuration available by selecting parts in the list above.
Recommended buffer configurations:
Carbine buffer system
Sprinco Blue spring with an H2
A5 Buffer system
Sprinco Green with A5H2 buffer
**Because we test fire every upper receiver group, you may see signs of “use” including carbon, brass markings, and lubrication. Its ready to shoot, not ready to show…**
Ryan (verified owner) –
Ive been extremely happy with the performance of the VMU upper. It is evident that Trajectory Arms really took the time to hand pick parts to ensure the perfect fit and finish. The work they did on polishing the feed ramps looks amazing, the fitment of the bolt into the chamber feels buttery smooth when going into battery, and the end result is an upper that has performed flawlessly this far and I have no doubts it will perform to the same level for it’s entire lifetime. All the unseen work they did to the upper (trying the receiver, bedding the barrel, tight fitting parts) are great for peace of mind for the longevity of the parts. This upper is going to be run hard and I have no doubts it will continue to perform to the highest level. It’s also awesome to have the option to change parts (like the forward assist or charging handle) when purchasing, I didn’t have to change anything when I got the upper. 10/10 would recommend using the VMU upper.