Rob suggested the channel might be to deep on selector but if no one else is having a problem <dontknow> .That was my first lower build.Went through the parts process of elimination on what went where.About the only springs that looked similar in lenght were takedown/pivot and selector.Use same lenght springs for takedown/pivot and other for selector.I got BAD selectors to replace just wondering for myself if I fukedup or what. <dontknow>