It is a good cartridge I have the similar wildcat made by Dedicated Technology called the 6MM DTi . It's the 6.8SPC with a 30 degree shoulder necked to 6mm and it's a nice round running 75gr VMax at 3275fps from a 22 inch barrel. The Hagar is designed to shoot the heavier bullets but the DTI is good if you are looking to shoot the 85gr or less bullet weights. Mine is a Predator rifle but I have shot Axis/ Whitetails too.
The 6mm Hagar seems to be a very capable round. The problem is that it is based on the original .30 Remington case, rather than the shortened one used for the 6.8 SPC. Hornady was the only company making original .30 Rem brass, and they announced a few month ago they were no longer going to make it. I went with 6mm SPC so that I could use 6.8 SPC brass and modified bushing dies. Costs about $20 for the bushing and expander to convert 6.8 dies to 6mm. I'll try to find the link I had to the parts numbers needed over the weekend.