Im currently serving overseas and when return i plan on doing some upgrading on my AR lower. I plan to share it (M&P 15 CARB) with my 16" upper M&P and a 20" upper in 6.5 grendel and im wanting some ideas for the different kinds of trigger assemblies that would best fit my needs. I use both uppers in hunting/tactical/longer range enviornments. I was thinking the  Geissele Super 3 Gun (S3G) trigger. Any ideas?

Geissele SSA-E. It has 3.5 lb pull weigt and is has two stages. I have on that I use for longer ranges and hunting with my 6.8. It's just about perfect for precision shooting, and I think it would fit your needs better than the S3G. The pull on the SSA-E is also light enough that you can slap through both stages for quick shots without feeling the second stage.

awesome thanks for the tip ill have to look into it.

SSA E I would say for long range hunting stuff......SSA  for regular duty/shtf set up is more than fine

thanks...also, i know you can shoot a 6.5 upper on a 5.56 lower but can you when the lower is a carbine model and the grendel upper is 22 inches long? will it affect performance if any?