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
I have shot tens of thousands of rounds of their 9mm and 5.56 FMJ offerings with no issues. It isn't the cleanest ammo but is far from the dirtiest. It is however reliable.
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.
I can only comment on the quality of their brass, since a friend and I load .577/450 Martini-Henry formed from their 24 gauge shotshell brass. It's really excellent.
I have shot hundreds of rounds of Magtech ammo in both 9mm and .40 S&W. I have had zero issues with it and would not hesitate to use it for practice and competition.