Windham Weaponry reintroduces the MGI Hydra

Windham Weaponry has entered a product onto the market, that is a reintroduction of a product that came out around eight years ago or so. It is also an expansion of their MCS1 upper receiver kits. The MGI Hydra was a proof of concept rifle that by changing out the bolt carrier, barrel, and magazine well, a shooter could switch from a number of calibers, from 5.56×45, 7.62×39, 9mm, and .45 ACP within literally minutes, by pulling out on a knob on the handguard, switching bolts, and then clicking in a new magazine well for the intended cartridge, with different adaptors for AK, Glock, AR15, and M3 Grease Gun magazines. There were a number of different versions as well, some in pistol form, and in more calibers. The product didn’t gain massive support, but it appears that Windham Weaponry feels that the company can make it work this time around, just in time for SHOT. They’ve added .300 BLK to the caliber availability and have expanded the types of packages that a customer can buy the conversion system in. The basic package comes with a 5.56x45mm and a .300 BLK barrel, that goes for $1738, called the RMCS-2. The RMCS-3 comes with a 5.56x45mm, .300 BLK, and 7.62x39mm barrel and goes for $2391. The RMCS-4 has all the above calibers, in addition to 9mm, and is going for $2971. All of these kits have the complete rifle in them.

Windham, ME – In one of the most exciting announcements to come from Windham Weaponry since its inception in 2011, the Company invites attendees of the 2016 Shooting, Hunting, and Outdoor Trade Show (SHOT Show) to visit them in booth #10376 to see their new multi-caliber AR Platform rifle series.

The Windham Weaponry Multi-Caliber System (MCS) is a groundbreaking new rifle that allows the user to convert between calibers by changing out the barrel, magwell, and bolt carrier group and utilize the same lower and upper receivers. The MCS is available in three configurations, and offers up to four caliber options in one AR platform rifle.

RMCS-2-Rifle-Kit-Web-med unnamed RMCS-3-Rifle-Kit-Web-med


Infantry Marine, based in the Midwest. Specifically interested in small arms history, development, and usage within the MENA region and Central Asia. To that end, I run Silah Report, a website dedicated to analyzing small arms history and news out of MENA and Central Asia.

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  • Reintroduce the AK-74 magwell, and I’d be in for one even if I need to mill the upper out a bit (just give me specs!). I’ve got a spare 5.45×39 upper sitting around that I’d like to do a build with, but I am tired of these weird AR-specific 5.45×39 magazines.

  • LCON

    What the first post was not a “Hail Hydra” Joke?!

  • Jsim

    It’s really cool but isn’t there gonna be a huge issue with having to sight it in every time you change a barrel and caliber

  • This might be a good time to point out that both Windham Weaponry and MGI can trace their heritage back to the original Gwinn Firearms, the manufacturer of the Bushmaster Arm Pistol.

  • thedonn007

    Can you use a standard upper on this lower?

  • Dracon1201

    This is less than interesting. For $3000 I could build 3 incredible uppers and put them on a cheap lower.

    • hking

      That was my reaction when I stumbled across the Hydra a few years back. Their “lower receiver” was only $100 but each magwell was $250, so if you wanted AK and AR you were looking at $600 for just the lower. Its a neat idea but not cost effective in the slightest when you can have another entire gun for less.

      Now make a kit that comes with the AR magwell, AK magwell, colt and/or glock magwell, and sell it for $300 I would be down like a clown.

      • nadnerbus

        This has been the problem with pretty much all caliber conversion systems I have seen so far. The concept is nifty, but not so necessary as to charge as much, or more than, just buying complete rifles in all of those calibers.

        If you sell something like this for, say, 7or 8 hundred bucks for the 5.56 version, then have the conversions available for 3 or 4 hundred bucks a piece, you might actually move enough units to justify the tooling. I just don’t see it moving for the price quoted, though. I’m sure Windham has done the number crunching better than I have, though.

        • Rick5555

          I agree with your comment. However, I don’t think Windham did do their number crunching. It’s easier for me to just get an individual rifle in the caliber. Walk into my gun room and pick one or the other, perhaps both firearms. And proceed to the range. For this sort of concept to take off and worth while to the masses. It has to be affordable and priced fairly. For $3K, I can pick up an AR in 5.56 and 300 black out, A decent AK. And get a Just Right 9mm Carbine or a CZ EVO and still have some money left over. Sell the kits for $500 and get what you want. And I think people would buy it. Sometime I think the firearms industry assumes everyone has buckets of cash to purchase their items. Though I can afford what I want. I still like to be assured the item was priced fairly. My Dad always told, me a quality product, don’t be greed. And always be fair in business and to your customers. Though I’m a surgeon at a University (Vanderbilt). I do have a manufacturing business that pertains to healthcare instruments And the business does well. Because, the items are quite affordable. Also, you tend to do more in volume of sales too.

    • JamesRPatrick

      You could buy three great complete rifles. Or five good complete rifles.

  • DIR911911 .

    well, send them out to vegas and let’s see how long it lasts

  • John Bear Ross

    Perhaps they can introduce a wider magwell that can take the Six8 Magpuls. I would also suggest a longer handguard that has optional rail mounting points. I don’t like being stuck with just carbine gas tube.
    I love the modularity aspect. Just need more options.


  • Arandor Thinnorion

    The headline is a little confusing. “Windham Reintroduces the MGI Hydra”

    The MGI Hydra has nothing do with Windham. MG Industries is a completely separate company that still produces their Hydra multi-caliber rifle system. Windham’s multi-caliber rifle system is the RMCS. So they are completely different products currently in production by completely different companies.

    It would be like having a headline say, “Burger King Reintroduces McDonald’s Chicken McNuggets”.

  • Phillip Cooper

    For that kind of money, I’d rather just buy entirely new rifles per caliber….

  • Unlicensed Dremel

    Carbine system – you’re kidding, right?

  • Arandor Thinnorion

    Just saw a photo of the MGI Hydra booth from 2016 SHOT Show. They must be pretty excited that Windham is re-introducing the product they (the MGI team) are their promoting. I wonder if MGI had to pay a fee to get Windham to re-introduce the MGI Hydra multi-caliber system rather than Windham promoting their own new MCS system.

    Wonder if there are any other cases of competing products promoting the other. Is Ruger re-introducing the S&W M&P 9mm?