Couldn't give you the exact gas port size, but will say my ddm4v7lw runs perfectly with an h2 buffer and blue sprinco when using pmc bronze and m855 - tested last round holdopen many times with the bronze to make sure the setup would work. Won't run wolf steel without constant undergas failures (never hold open, often FTF), but I haven't tried with stock springs and h buffer. DD does say not to run steel, so....

