The most distinct and unique feature of the Super Lower is the large support rib on the left side of the lower. This greatly increases the strength and stiffness of the buffer tower. Unfortunately another large rib cannot be added to the right side of the lower because it would interfere with the forward assist on many upper receivers. The result is that the right side becomes the the new weak spot of the buffer tower area. The main goal of V3.0 is to fix that – While still maintaining compatibility with a wide range of uppers.
Before we dig into the details I want to say, if you have already printed an older version of the Super Lower, such as V2.7 or V2.8, then I highly recommend you reprint with V3.0. The older versions worked great, and still will. But V3.0 is better. You can download the V3.0 files over on the downloads page.
I made several improvements with V3.0. One of them is that the bolt hold open area has been redesigned. But the most important change was the redesign of the right side. Below you can see a photo of V3.0.
It may not look very different from older versions, but the change will be more obvious in the below photos.
The weak spot on older versions was compounded by the rear take down pin hole resting very near to the surface on the right side, creating a stress riser that would further weaken the right side. In the above photos you can see that around an eighth inch of material has been added to the right side above where the rear take down pin hole ends. Also a small rib has been added above the right side that helps to increase strength, while not interfering with the forward assist.
The material has been added in such a way so as to not to effect function. The rear of the buffer tower has the same profile as older versions, so the same stocks and clamp will work fine.
Something that quite a number of people have requested is an ambidextrous lower. I don’t think an ordinary single ribbed lower would be strong enough if the right side was cut down to allow a ambidextrous selector switch to be used. However that does not mean there is not another way to do so.
I think that the best way to design an ambidextrous lower is to use two full sized reinforcement ribs, one on each side. This would have the caveat that only slick sided and side charging uppers could be used. But the extra rib on the right side would add enough strength that the right side below the rib could be made slim like the left side is now. And any ambi’ selector could be used at will. That’s a project to do after the AR-9 is done.
Of course these changes can, and should, also be made to the LR-308 Super Lower. That will problebly result in the V2.0 LR-308 Super Lower. Though no promises on when that will be released 😉
Let me know what changes you would like to see with the Super Lower. And be sure to download V3.0!