Review: GWACS Armory CAV-15 MKII Polymer AR-15 Lower Receiver

The CAV-15 Lower (and eventually the CAV-15 MKII) from Cavalry Arms was the first commercially successful polymer lower receiver for the AR-15. It was either the best thing since sliced bread or a complete waste of time depending on who you ask. I have always wanted to try one but I feared that I had missed my chance when Cavalry Arms was shut down a few years ago. Thankfully, I got a second chance when GWACS Armory purchased the CAV-15 MKII molds and IP in order to start producing these lowers again.



The GWACS Armory CAV-15 MKII lowers are nearly identical to the original ones manufactured by Cavalry Arms. These lowers are made completely from polymer and have an integrated grip and A1 length stock. They utilize a standard AR-15 lower parts kit and any standard upper receiver group. Nearly every part will interchange except the CAV-15 MKII uses proprietary take down pins. The GWACS Armory version features a new, thin, hard anodized butt-plate that makes it slightly shorter than the original.

The original CAV-15 MKII was popular for 2 main reasons – light weight and wide variety of available colors. Its polymer construction make it lighter in weight than a standard receiver with an A1 stock by about a pound and lighter than most standard receivers with a collapsible stock by a smaller margin (.2 to .4 pounds depending on the stock). The polymer construction also allows these receivers to be made in just about any color and a wide variety of them are already available.

GWACS Armory CAV15 MKII Ejection Port Side

GWACS Armory CAV15 MKII Trigger Guard

Observations from Use

When I first found out that I would be testing the CAV-15 MKII, I spent some time figuring out how to best configure an upper to utilize in testing. This lower has an integrated fixed stock and light weight which I felt made it well suited to hunting and competition applications. So, with the help of, I reconfigured an upper, that I had already established as reliable, into a relatively light weight and practical rifle competition or hunting AR-15 upper to use on the CAV-15 MKII.

This lower really is light weight. I put it in the hands of other shooters during my testing and many of them commented on the weight as soon as it was in their hands. Its light weight is immediately noticeable if you spend time around AR-15s. If I was building an AR that I expected to be lugging around creation in search of game along with everything I needed for several days in the bush, I would I definitely give this lower a look so I could save some weight.

The integrated fixed stock looks pretty standard but it is kind of interesting internally. There is no aluminum receiver extension. The buffer rides directly on internal plastic rails. These rails create a lot of void space inside the buffer tube that allows for debris to stay clear of the buffer which, theoretically at least, could enhance reliability. This system has been tested past 50,000 rounds and it holds up fine.

GWACS Armory CAV15 MKII Buffer Tube

GWACS Armory CAV15 MKII Guts

I should also mention that the buffer tube is sized to use carbine buffers and springs even though, externally, it looks like it would use a rifle buffer and spring. This seems like a small thing but it is actually a great feature when you consider the variety of weights that carbine buffers are available in. This makes it possible to tune your buffer weight more easily based on variables like ammo choice, gas system length, etc.

The grip is comfortable. It has some nice contours and a subtle thumb shelf. GWACS Armory gave the polymer a light pebbled texture that is actually quite grippy. If you need more grip (I didn’t) you can add a Hogue Hand-All for GLOCK, a bit of bicycle tire inner-tube, or you can stipple it.

While this lower wouldn’t be my first choice if I ever expected to use it while wearing armor, I was somewhat surprised to find that it actually worked pretty well even with the fixed stock. I normally like to shorten my stock a bit when using a plate carrier but this slightly shorter than A1 stock was fine for me as long as I was wearing a carrier that would allow me to get the stock into my shoulder pocket instead of putting it onto the armor. The aggressively textured aluminum butt plate helped quite a bit. It absolutely locks the stock in place. There will be no slipping with this butt plate.

GWACS Armory CAV15 MKII Buttplate

Many of the features that cause people to automatically dismiss the CAV-15 MKII are the same features that make it a viable (maybe the only viable) polymer lower on the market. The integrated stock and grip make it difficult to customize and a collapsible stock is very nice to have if you wear armor. However, if these items weren’t integrated, this lower would be prone to the same breakage that is seen in other polymer lowers that exhibit where the grip screw and receiver extensions screw into the lower. The CAV-15 MKII has a reputation for being very strong. At least one was run over by a truck accidentally and it continued to function.

The magazine well is nicely flared and allowed every magazine type (multiple generations of PMAGS, Tango Down ARC mags, and GI mags) that I tried to drop free easily. As nice as the mag well is, it does seem like there is enough meat there that it could be flared even more aggressively.

My sample does have some fit and finish issues. There are several places where there is quite a bit of flashing left behind from the molding process including the bottom of the trigger guard, bottom of the grip, and the bottom of the magazine well. So far, these have only been cosmetic issues however, it would be nice to see at least the mag well cleaned up to a great extent to reduce the potential for magazines to hang up during a reload. You can tell that great care is taken to remove the flashing in more visible areas but the less visible parts need some work.

GWACS Armory CAV15 MKII Magazine Well

GWACS Armory CAV15 MKII Take-Down Pins

The take down pins that came with my sample have very poor finish. One of them appeared like it may have been used before. The black finish is worn off and the pins are left showing quite a bit of bare metal now. Most of this finish wear comes from the fact that they are very difficult to inset and remove on my sample lower. I couldn’t do them by hand at first and while they have gotten a bit looser over time, they are still quite tight and a tool is often needed to drift out the rear pin.

NOTE: GWACS Armory has addressed the issue with the finish on the pins. All lowers now ship with improved pins that do not have these finish issues.

The CAV-15 MKII as delivered gives you very few good sling mounting options if you plan on using a modern 2 point sling or single point sling. If you aren’t handy, your best bet is to get in touch with Trooper-Gear who makes a sling specific to this lower that works well. If you are handy, you can easily modify the lower with an Impact Weapons Components QD Micro MOUNT-N-SLOT (remember to use the discount code “triggerjerk” for 5% off) to serve as a rear sing mounting point. There are also a variety of other home brew solutions out there that are very easy to execute.


The IWC QD Micro MOUNT-N-SLOT is an excellent addition to this stock.

It would be interesting to see GWACS Armory introduce CAV-15 MKIII lower that featured improved sling mounting options, a shorter butt stock, a more vertical grip angle, and a more aggressively flared magazine well. Something like that could weigh even less and better support a more modern stance or shooters of smaller stature.

Wrap up

I guess you could say that the CAV-15 MKII surprised me. I originally thought that the fixed stock would limit its usefulness for certain applications, but I found that it performed admirably even when wearing armor. There are some nagging fit and finish issues and the take down pins on my example are extremely tight, but the lower still performed. I honestly didn’t think that I would like it as much as I do.

Those who write the CAV-15 MKII off without exploring applications that these lowers excel at are missing out. This shouldn’t be the first choice for a SWAT cop, but if you need a reasonably priced AR-15 lower that will keep weight to a minimum, these are definitely worth a look.

Check out If you enter the discount code “JERKINGTHETRIGGER” at check out, you will receive a 5% discount. GWACS Armory can usually ship a lower to you within about 4 days of receiving your FFL info even in today’s high demand market!

Disclosure: This lower was provided, free of charge, to me for review by GWACS Armory.

Special thanks to for providing some of the items used to complete this review.

GWACS Armory CAV15 MKII Roll Pin

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17 Responses to Review: GWACS Armory CAV-15 MKII Polymer AR-15 Lower Receiver

  1. TomcatTCH December 25, 2012 at 20:41 #

    I have three Cav Arms pattern lowers. Two Cav Arms and one Eagle Arms that Cav made OEM for Armalite.

    I like em a lot, especially for use with a .45 ACP upper and grease gun magazines.

    • Matt December 25, 2012 at 20:48 #

      Good point. The magazine well is sized perfectly for use with pistol caliber magazine adapters.

  2. Thomas Weddell January 11, 2013 at 03:26 #

    Interesting product. Might have to think about it for a future build.

  3. Eric January 14, 2013 at 18:58 #

    Not great for showing off, but for hunting jackrabbits it’s the perfect solution.

    Make pink ones for my daughters, please!

  4. Kenny Wheeler / AlfaDog Gun Works January 16, 2013 at 09:00 #

    I have only glanced at this type of lower in the past, and honestly at the time I completely dismissed em due to good old steel and billet lowers being readily available. I kinda stored them in the back of my mind in case a build for a beginner or maybe a strictly target or varrmet rifle. Now after reading your fantastic review, these lowers seem like a very viable option for the drouth of standard metal peaces. This is really the first time Ive actually spent this much time checking out the design and details of the one peace plastic lower, and as a Gunsmith and hopeless modifier, I am starting to see some decent possibilities for some pretty cool, and possibly slightly “ventilated” builds with one of these things. I would love to be able to get my hands on one of these for a day or two to really check out the fit and finish, and see where it can be shaved down some without loss of structure. Basically Im thinking if was built the way Im thinking by just seeing the photos, I already kinda see 2 maybe 3 builds here. The main thing Im really interested in that I dont think was touched on here is a little more about the construction of the A1 stock itself. For instance, are they solid or hollowed? Other than the buffer tunnel obviously. It looks as if the stock may be slightly “beefed up” in a couple of areas to add strength. What is the over all feel of the just bare lower itself? Does it feel solid? Does it have that cheap hollow feel to it? Does the buffer tunnel extend all the way through the length of the stock? If not any way of letting me know how deep it does run and how long is the length of pull over all? Like I said, I would love to just get one in my hands for a few hours before I fully commented because I at that deal or no deal point based on these and a few more questions I have. I need 6 stripped lowers, if possible, right now and Im really thinking I could go this direction if it’s right. Ok, I’ve rambled for long enough now…Im flipping over to the GWACSArmory site now and maybe I can bug them too! Would love to have a few of these questions answered if possible, at your convenience of coarse. If your still reading and haven’t fallen asleep, or just decided the Hell with it and moved on, well thanks! Any help here from any that may have Intel would be greatly appreciated. Over.

  5. Frank Zumpf January 20, 2013 at 20:05 #

    Polymer frames are super frames, lightweight, long lasting.I have a polymer frame on my 9mm auto pistol

  6. Guy Schmidt January 20, 2013 at 20:13 #

    do they come in real tree???

    • Matt January 20, 2013 at 20:15 #

      I don’t think so but it would be pretty easy to send it out for hydro-coating. You can always contact GWACS Armory to find out.

  7. VIctor Solis January 21, 2013 at 17:34 #

    What is the muzzle break on the rifle in the first picture in this thread. i like the slanted aspect of it. Anyone know or direct to the maker.

    • Matt January 21, 2013 at 19:11 #

      It is the Proto Tactical Z-Comp.

  8. Rick February 22, 2013 at 20:49 #

    They are in full swing production. I have 2 completely populated lowers on the way.


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