MARS® Clone A4 Upper

Meet The MARS® Clone A4 Upper: A Classic Reborn

Looking to add a serious upgrade to your next AR build? The MARS Clone A4 Upper is right at home whether you're tackling the range, embracing the look of a classic service rifle, or just want that perfect blend of function and style. The team at Retro Arms set out to make the modular ambidextrous rifle system upper as true to vintage inspiration as possible, yet packed it with fresh engineering. If you're a collector, builder, or everyday shooter, this upper will grab your attention from the very first look.

Why The MARS Clone A4 Stands Above The Rest

For some, it's all about authenticity. For others, it's the desire for flexibility on the field or at the bench. This MARS A4 Upper for AR-15 offers both: period-correct details and modern usability. Our RA MARS upper assembly isn't just a replica; it's a carefully crafted piece built to last and ready to evolve with your needs.

• Authentic MARS Clone A4 upper receiver profile for historic accuracy
• Fully ambidextrous AR-15 upper receiver controls for right- and left-handed shooters
• 12 inch HBAR A4 upper barrel for compact power
• Versatile low-profile handguard upper for a variety of grip styles
• Reliable, forged mil-spec 5.56 upper receiver construction
• Perfect fit with other vintage AR-15 upper parts
• Designed for easy builds into a true M16A4 clone upper receiver

Designed For The Enthusiast

We know AR fans have high standards. That's why our modular ambidextrous rifle system upper is cut, finished, and assembled by folks just as particular as you are. The heart of this upper is the 12 inch HBAR A4 upper, chosen for its classic lines and compact, maneuverable profile. Pair that with the sophisticated ambidextrous AR-15 upper receiver design and you get a platform that works with anyone's shooting style.

All The Looks, All The Function

There's something special about a compact M16-style upper receiver. Maybe it's the nod to military history, maybe it's the ease of use at the range. When put together as a complete retro AR-15 upper assembly, this upper shines.

• Traditional styling meets new-era comfort
• Supports most vintage AR-15 upper parts and modern add-ons
• Seamless fit for anyone making a true M16A4 clone upper receiver

Built To Mil-Spec Standards

Reliability matters. That's why the mil-spec 5.56 upper receiver platform serves as the core of this design. Precision machining and tough materials mean your RA MARS upper assembly is ready for the field, the range, or a spot in your display. We've matched it with the best vintage AR-15 upper parts for full authenticity.

A Custom Experience From Start To Finish

Building with the MARS Clone A4 Upper Receiver gives you endless possibilities. Whether you want a faithful M16A4 clone or a shooter with modern flair, you're covered. The modular ambidextrous rifle system upper lets you swap out internals or controls with ease.

• Compact, retro-inspired 12 inch HBAR A4 upper
• Ergonomic ambi setup for both left- and right-handed use
• Flexible low-profile handguard for less bulk and more control

Style And Utility: The Heart Of The Design

Many builders want a balance — a piece that looks at home next to collectibles, but shoots like a top-level modern rifle. The compact M16-style upper receiver manages just that. You'll feel the inspiration the minute you handle our RA MARS upper assembly. Lightweight, solid, and detailed where it matters.

• Works well with historical or tactical setups
• Mixes vintage AR-15 parts for the retro build of your dreams
• Designed to create an authentic retro AR-15 upper assembly

Everything You Need, Ready To Go

Putting together the MARS A4 Upper for AR-15 is simple with the right kit. You get a mil-spec fit, a sturdy mil-spec 5.56 upper receiver, and real flexibility. Plus, a low-profile handguard keeps things neat and quick to handle. We've tested all combinations to ensure each ambidextrous AR-15 upper receiver operates smoothly and feels natural to use.

Our shop stocks replacement and upgrade vintage AR-15 parts so your project never stalls. Whether you want to upgrade a classic or kick off a new build, this is the perfect place to start.

The Modern Classic, Yours to Build

With the MARS Clone A4 Upper Receiver, you get the best of both worlds: classic military-inspired styling and modern performance. The modular ambidextrous rifle system upper is built for those who want a true M16A4 clone without compromise. Add in the compact 12" HBAR A4 Upper, and the result is a standout compact M16-style upper receiver.

Ready to make your next project unique? Dive into the world of retro AR-15 builds with our RA MARS Upper Assembly and enjoy the process as much as the result. Your perfect MARS A4 Upper is waiting.