Spike's 6" upper, ramped bolt, WolfeXP spring, on a Spike's pistol lower with a CMMG 2 stage trigger and CP mag block.
After the first round is fired the bolt will chamber another round but will not cock the hammer. I switched the upper to a Spike's lower, RRA block, same spring and buffer only with a White Oak modified RRA 2 stage trigger and it ran great.
To confuse things more I also have a RRA 16" carbine on a Spike's lower, CMMG 2 stage trigger with a standard .223 spring and buffer and a RRA block. It ran without a hitch. I even switched out the bolts between guns and the pistol upper wouldn't run with either bolt. My question is is, what's up with the pistol configuration? Any suggestions would be appreciated.