I have just got my AR15 put back together after replacing the lower to make it California legal. It started as a DPMS "Bull 20" I replaced the lower with a Smith and Wesson lower and reinstalled all the DPMS trigger and other lower parts from the original. It chambers a round fine and if you do not pull the trigger it will eject the unfired round as it should. I have three problems first it does not eject fired casing ie the action does not cycle. Second when you do fire a round it takes ALOT of force to pull the charging handle to the rear to eject the fired case. Lastly the rear pin is a beast to get in. I have already checked the gas tube from the block to the action. I have looked over the carrier group and all looks to be good and I have cleaned and re-lubed everything ANY HELP would be great. I will post pics if you need them.