The Optimus lower is also somewhat longer than a typical forged lower. This creates a longer path for magazines to travel into the gun when seating. Therefore if the magazine exterior dimensions change such as with the SureFire 60 and 100 round aluminum body magazines, the mag will not seat. The flare of the SureFire magazines hit the magwell on the lower and do not allow these high capacity magazines to seat.
If you would like to see the process for completing your own 80% lower click HERE for my video on the Whiskey Arms 80 percent lower.
|This is the configuration we used for most for the testing. It proved to be the most fun when shooting fully automatic. The recoil and muzzle flash combined with the concussion from the muzzle break got high marks on the fun factor scale.|
|This is how I received my 80% lower. In the photo you can see there is no trigger/hammer pin holes drilled. Also, the fire control pocket for the LPK (Lower Parts Kit) is not milled. This makes the lower not a gun by the ATF rules.|
|Front view of the Optimus Defense lower with the 100 round AR15 drum magazine inserted as far as it will go.|
|Optimus Defense 80% Billet Lower (Left) and Typical Forged AR15 Lower from Colt (Right)|
|Front view of the Optimus Defense Lower with a SureFire 60 Round Mag inserted as far as it will go.|
|Rear view of the Optimus Defense Lower with a SureFire 60 Round Mag inserted as far as it will go.|
|Mag catch removed from the lower so you can see how the SureFire double stack magazine does not travel far enough upward into the magazine well for it to catch and fully seat in the lower.|