It is my understanding that the Fostech Echo is generally the superior product. However, as I understand it the Fostech Echo requires it's own proprietary bolt carrier. Additionally I'm, guessing that precludes it from being used in 9mm as 9mm AR's are generally blowback and have one piece bolt and carriers.

How would this be different as it relates to the current gen 2 offering from Franklin Armory?

I just have to find a way to make one of these things work in 9mm.

HAVE TO!!