Well I've used the standard rifle length buffer and spring with no issue, then bought the SCS which comes with the fifle length spacer. I was going by what JP customer service recommended which was an (H2 setup). For the $$ I want to make it work. This didn't completely work either. The gun runs better than with the steel weights it comes with, just not 100%. Sorry if it seemed"complicated", I was trying to provide all the info of the build. It did function better with the 2 tungsten weights on the SCS. Again, any useful information would be appreciated. Questions? Ask. Thanks.