As a dedicated enthusiast of firearms, I am always excited to try out new products and explore the features they have to offer. Recently, I had the opportunity to test the Aero Precision M4E1 Superlative Arms Piston Complete Upper Receiver Groups, and I must say, I was thoroughly impressed. In this review, I will share my experience with this upper receiver group and provide an in-depth analysis of its pros and cons.
The M4E1 Superlative Arms Complete Upper Receiver Groups, built by Aero Precision, are designed to integrate seamlessly with the Superlative Arms Piston Kit. This upper receiver was spec’ed out by Brownells and Aero Precision, ensuring a perfect match and optimal performance. One of the standout features of this upper receiver is its ability to vent hot gasses and debris at the gas block, rather than in the receiver like a traditional gas impingement AR-15. This not only improves reliability but also makes cleaning the chamber area much easier.
The adjustable Superlative Arms Gas Block allows for fine-tuning of the gas setting, providing shooters with greater control over their AR-15’s performance. The adjustment can be easily done through the front of the handguard. Additionally, the gas piston can be removed through the front of the handguard, simplifying maintenance processes.
The M4E1 is Aero Precision’s Enhanced Upper, which offers a rigid interface with the MLOK M4E1 Handguard. The handguard itself boasts a full-length Picatinny top rail, machined-in QD (quick-detach) sockets, and MLOK accessory slots at the 3, 6, and 9 o’clock positions. The combination of these features allows for easy customization and flexibility in mounting accessories.
The bolt carrier of this upper receiver group features a slick DLC (diamond-like coating) finish, while the bolt itself has a hard and slick nitride finish. This ensures smooth operation and enhanced durability. Additionally, the bolt undergoes magnetic particle inspection, guaranteeing the absence of microscopic defects.
Available with barrel lengths of 10.5, 14.5, or 16 inches in 5.56×45 caliber, the M4E1 Superlative Arms piston complete upper receiver group offers options to suit different preferences and shooting styles. For those seeking an even longer barrel, there is also an 18-inch variant with a stainless steel barrel, which includes an AR-15 carrier.
During my testing, I encountered a minor compatibility issue when trying to mount this upper receiver on an Aero Precision Ambidextrous lower. The rear takedown pin could not be fully inserted, suggesting misaligned pin holes. However, when I switched to my M&P15 lower, the upper receiver fit without any issues. This raises the importance of ensuring compatibility before purchasing or considering alternative lower receivers.
Another minor issue I noticed was that the dust cover sometimes required more force to close smoothly. The detent appeared slightly too long, causing the dust cover to jam. This may be a minor inconvenience for some users and can easily be rectified with slight adjustments.
In terms of performance, I experienced mixed results. The upper receiver performed flawlessly for the first 20 rounds of factory PMC XTAC ammo, delivering accurate shots. However, after prolonged use, the gas block became loose enough to rattle around the barrel. This was likely due to improperly torqued and secured set screws locking the gas block to the barrel. While this was disappointing, it is important to note that these issues may be isolated cases and not representative of the product as a whole.
This upper receiver is designed to be compatible with most AR-15 lowers. However, there have been some reported compatibility issues with certain lower receivers, so it is essential to ensure compatibility before making a purchase.
Piston-driven systems, like the one in the M4E1 Superlative Arms Piston Complete Upper Receiver Groups, offer several advantages over traditional gas impingement systems. These advantages include reduced fouling in the receiver, improved reliability, easier cleaning, and more consistent cycling.
Yes, the Superlative Arms Gas Block offers easy adjustment through the front of the handguard. Similarly, the gas piston can be easily removed through the front of the handguard, simplifying maintenance procedures.
Yes, the M4E1 Superlative Arms Piston Complete Upper Receiver Group is available with barrel lengths of 10.5, 14.5, or 16 inches. Additionally, there is an 18-inch variant with a stainless steel barrel.
The bolt carrier features a slick DLC (diamond-like coating) finish, while the bolt itself has a hard and slick nitride finish. These finishes provide smooth operation and enhanced durability.
In conclusion, the Aero Precision M4E1 Superlative Arms Piston Complete Upper Receiver Groups offer a strong combination of performance, reliability, and customization options. While there have been reports of compatibility issues and some minor inconveniences, the overall package is well-designed and provides an excellent platform for AR-15 enthusiasts. I highly recommend this upper receiver group for those seeking a piston-driven system and a versatile upper receiver for their AR-15.
