Issue with 9mm AR build

[spederman]

I'm in the middle of putting together a fun little plinker and running into some trouble. I'm using a complete upper from a Colt 6951 and a dedicated 9mm lower (cmmg MK9). The upper has a ramped bolt which is what cmmg lower is supposed to be made for since it's got a regular AR hammer. Everything goes together and fits perfectly except the charging handle is extremely tough to cycle. You have to put the butt on the table and pull the charging handle with both hands. Once the bolt gets free from the closed position, then it slides easier but still not as smooth as it should be. Any idea on what to check to figure out what's going on?

[Denny]

Make sure there's not a slight bend on the charging handle. Even the slightest wave (naked to a quick view) can make it a PITA. Does it do it with or without a round?

[spederman]

Figured it out. For some reason the bolt catch height on the Cmmg is a lot taller than the standard colt bolt catch. I'll have to pick up a colt spec or shave down this one