I just put together a 9mm ar. A buddy gave me a 16 inch upper without a bolt. I bought a CMMG bolt, Hahn mag adaptor, and 9mm buffer. I put all it all together with a collapsible stock with stock spring and a Chip Mc Cormick drop in trigger . What is happening is 1 out of 30-90 rounds the hammer won't cock. when it does run it like hot loads.(hand loads) seems to not cock more with light/meduim loads. Also the bolt seems a little tight fitting to the upper. I oil it heavy hoping it will break in and lossen up some.

Any advise on what I should do?

From looking at pics, the hammer on your CMC trigger is notched, which won't work with a 9mm bolt.

I concur: notched hammers don't work well with 9mm bolts.  The bolt gets caught on the notch and you have a problem.  Try a FCG with a rounded hammer.