The WWSD project initially used two different uppers, one from VLTOR and the other being AERO. We looked for uppers that specifically included the brass defector but omitted the forward assist.
After using both rifles (and different uppers) extensively, we have standardized on the Aero upper as it does not interfere with our ambidextrous controls and is slightly lighter than the VLTOR equivalent.
The VLTOR upper is an excellent component, but it just did not fit perfectly into our WWSD project's goals.
This video discusses all of this and more.
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