Is this rated for in wall use?
It is rated in wall use and features thicker gauge conduits and isolation spleens that reduce cross-talk and system noise.
Will this be a good cable for a 300ft run through underground conduit from house to barn?
Most Cat6 cables run well without noticeable signal loss up to 100 feet, this cable is 1000 ft long, but if you are running 300 you may have some signal loss. We can help with getting you a signal boost to split the length by 150ft. twice.
Is it pure copper or cca?
It is solid annealed bare copper (oxygen free)
Is the cooper solid or stranded on the inside?
The cooper is solid on the inside.
What does CM Mean?
It stands for "Communications Multipurpose" cable, which indicates that the cable is a communications cable suitable for in-wall installation.