Mega Arms GTR-3S AR15 Billet Lower Receiver Review
Once you have your first AR15, you start to have the urge to build up your own AR via a kit, via individual parts, or at least upgrade the cool factor of your current AR. At some point the ultimate word in upgrade hits your lips... “Billet”. As you may know most AR15/M4 upper and lower receivers are made via forging which are typically forged from 6061 or 7075 aluminum into a near finished state and then finished per specification or desire of the builder. In fact there are only a small handful of forging companies in the US that make all the forged uppers and lowers for the various “AR manufacturers”. The result of forging is indeed a durable part which has stood the test of time, however as most forged receivers are made by only a couple folks there is little or no differentiation between the brands with the exception of grade of quality.
CLARIFICATION ON FORGING VS. BILLET
Forging itself has some mistaken assumptions. Two identical parts made from the exact same material with one being forged and the other being billet machined or cast, the forged part will be typically stronger. That said once you start changing the design a bit or change the material formula even slightly between the forging and billet parts, that strength margin can easily lean onto the side of the billet part. Advanced AR lower receiver designs such as the Mega Arms GTR-3S, have extra reinforced areas and features such as an integrated trigger guard thicker rear carrier/tube mounting area that all adds strength. When you also take into account some forgings are not using the top end 7075-T6 aluminum, the Mega Arms GTR-3S starts to make more sense than most forged options. If you are set on a forged receiver, Mega also has a $130 forged receiver line as well.
If you want custom cool features then you have to look to receivers made of billet. There are a variety of manufacturers making AR Billet receivers, however one which has become known for ultimate high quality is Mega Arms. Their billet receivers are entirely milled from a solid block of 7075-T6 aluminum and the result is a higher tolerance and much tougher part than what you find in forged receivers.
ABOUT MEGA ARMS
Mega Arms was founded by Mega Machine Shop which is a very high “zero tolerance” machining and fabrication manufacturer of aerospace products for folks like the US Government and your friendly neighborhood NFA Ordnance manufacturers. As you can image, precision is the name of the game when you are dealing with this type of manufacturing. Mega Machine Shop is far more than a small shop with a couple CNC machines. These guys specialize in the wild capabilities of precision 5-axis machining within their 22,000 square foot facility. It was natural at some point that someone would ask whether they could produce custom billet AR receivers and so it was on that day Mega Arms was formed. Today they have a large array of AR15 and MA-TEN (AR 308 format) upper/lower receivers in a variety of configurations from fairly tame to fully custom ambidextrous pieces. They also make a drop in custom trigger assemble and a number of other super premium AR accessories which I hope to review in the future.
THE MEGA ARMS BILLET BUILD
For my DPMS Oracle kit build and to test my Model 1 Sales Upper kit, I was in need of a lower receiver to complete the builds. Typically a stripped forged lower receiver can be had for $100-$150, however my intent was to make this lower the test bed for many upcoming reviews... sadly vanity played a bigger part than your would imagine and being unique is why I chose the Mega Arms GTR-3S Billet AR15 Lower Receiver. In the Mega Arms lower receiver line up the GTR-3S is the most affordable of their billet receivers... for $206 is was hard to pass up on.
FINISH & FIT
Mega uses a hard Type-III anodizing which provides a 60 Rockwell hardness finish and was perfectly finished inside and out. It is tough to gauge that this guys 60 Rockwell Anodizing finish looks better than this guys, however consistency of the finish and color is usually an indicator and this was the most consistent finish I have seen yet on an AR receiver. As with any AR receiver manufacturer they have to be cautious about how wild they get with their designs as they still need to marry to what-every upper receiver someone bolts on, but I think Mega took the right path with all the features packed in below the marriage line. The Mega Arms GTR-3S Billet AR15 Lower Receiver proved to be perfect for the build and I had no fit issues throughout the build process of either of the DPMS or Model 1 Sales kits.
FEEL & FEATURES
There are some features which make this lower receiver a little more comfy to operate. The front of the mag well is has little grip lines milled in and when combined with the larger flared magwell provide your weakside hand the ability to lock in a little better than the standard AR lower. The extended trigger guard is a welcome addition to any build and provides some serious cool points aside from the obvious ergonomic upgrade. The magazine well is heavily flared and would definitely be my choice if I was going to compete in 3-Gun or other speed based competition. The over-sized magazine funnel of the Mega Arms GTR-3S Billet AR15 Lower Receiver just seemed to suck magazines in. Another unique feature is the nylon tipped tensioning screw which eliminates all play between the upper and lower receiver in even the loosest upper to lower receivers fits. This little part can lock everything down and really help increase accuracy if you have movement between the receivers. The Mega Arms GTR-3S Billet AR15 Lower Receiver design itself is a very cool edgy modern look that in my opinion really updates the rifle all while still merging perfectly with any upper receiver.
In addition to the DPMS Oracle and Model 1 Sales Dissipator kits, functional testing was also done with a number of uppers I had on hand including: Rock River Arms, Spikes Tactical, Delton, Ruger 556C, and S&W M&P15. I experienced no feeding or functioning issues with any of these uppers throughout testing so my guess is that regardless of the upper attached to the Mega Arms GTR-3S Billet AR15 Lower Receiver there should be no issues.
Mega Arms offers a wide array of AR uppers, lowers and parts that fit in between including a very trick looking $139 forged receiver and a monolithic upper receiver unlike any other you will find. Ordering was easy and only required that my local FFL dealer do the common practice of faxing over their FFL license to Mega after I paid for the lower receiver. The receiver was shipped to my local dealer and I took receipt and completed all typical paperwork. All an easy process. From what I have seen so far this will not be my last Mega Arms receiver and am certainly impressed and looking forward to using their parts in future builds.
MANUFACTURER STATED SPECS
• The Mega Billet Lower features a clean, new, custom look unlike any of our competitors.
• Machined from billet 7075-T6 aluminum vs. the more commonly used 6061 for a 70% increase in strength.
• Integrated trigger guard for added functionality, and strength.
• Lower features a nylon tipped upper tensioning screw.
• Magwell features an enlarged bottom flare and inner chamfer for easier magazine insertion.
• Butt Stock attachment feature fortified for added strength in high power applications.
• Black Hard anodized with a surface hardness of 60 Rockwell.
• GTR-3S Matches standard forged upper receivers.
• 8.9 oz.
• Part# M0500 M.S.R.P. $206