Just put a 6 position stock on my 20" AR15 and would like to know what buffer will work best with all bullets weights
TX.......Buckey

With a 20" barrel, I would try a standared "carbine" buffer. The heavier buffers generally come into play when you are dealing with shorter gas systems, alternate calibers, etc. The rifle length gas system is pretty forgiving.

The carbine extension tube size requires a carbine buffer. If you need more buffering then you play with different weighs with the correct size buffer for your AR.

What has to do with shorter barrels, or lets say barrels of different lengths is the distance the gas port is from the chamber and the size of the gas port hole....not the buffer,but the buffer does fine tune it.

Thank you very much.