Windham Weaponry MCS Multi-Caliber Uppers

Richard Johnson
by Richard Johnson
Kit MCS2

Windham Weaponry announced new uppers that allow the shooter to quickly change calibers from 5.56 NATO to either 300 BLK or 7.62×39. The uppers are called MCS, or Multi-Caliber System. Currently, two are being produced: MCS1 and MCS2.

The MCS1 has a complete 5.56 NATO upper assembly, and comes with a swappable barrel for the 300 BLK. The MCS2 has a complete 5.56 NATO upper and 7.62×39 quick change barrel, plus a bolt carrier group and magazine for the Russian cartridge.

Readers may notice that the forend retaining system looks similar to the system used by MGI on the Hydra line of rifles. I exchanged e-mails with a Windham Weaponry representative about the new uppers. He confirmed that the Multi-Caliber System uses technology licensed from MGI, and that the two companies have had a long-standing association.

The MCS1 has a suggested retail of $899, while the MCS2 has a suggested retail of $999.

Richard Johnson
Richard Johnson

An advocate of gun proliferation zones, Richard is a long time shooter, former cop and internet entrepreneur. Among the many places he calls home is

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  • Roguetechie Roguetechie on Aug 29, 2015


    I have a hydra I've been using for years, it's a good gun all around. Personally though I won't use any bolts other than super bolts which I'm not sure Harrison makes them anymore, but I bought several long ago that I have in my parts stash still.

    I can't vouch for the subgun setups though.

    Personally I can't wait for Someone to do A X39 G2 Mutant mod.

  • Supergun Supergun on Sep 12, 2015

    Can you operate 7.62x39 on an AR 15 lower?