Yes it is. From the Magtech home page:
"Magtech is a member of CBC Global Ammunition, the holding for a group of companies internationally active in the ammunition sector: CBC Brazil, Magtech Ammunition USA, MEN Germany and Sellier & Bellot Czech Republic." Rick
These guys use Magtech by the truckload and swear by it. They say it is as reliable as anything they've had. If it were particularly dirty, they wouldn't use it. They have to keep the guns clean and the amount of ammo they go through is staggering.
I have shot several hundred rounds of their 5.56 77gr as well as both supersonic and subsonic 300 blk with no issues. The 5.56 has grouped very well out of several barrel lengths. I will be buy more if I am lucky enough to find some at a reasonable price.