Here is the problem with all of the 338's. First of all people tend to forget that 30 caliber bullets are available in weights heavier than 180 gr. The 338's are an attempt to shoot heavier bullets than are commonly used in the 30 cals, but compared to the 30's they just don't make a hole enough bigger to matter. That extra .03" is just enough to mess up the aerodynamics.
If you compare 338 Fed to 308 and 30-06 with 200 gr bullets in all 3 the 308 is slowest at about 2500 fps, the 338 Fed is next at around 2600 fps and the 30-06 will shoot them at around 2700 fps.
The extra 100 fps gives the 338 a 200 ft lb edge at the muzzle. But the better BC's of the 308 (.588 vs .415), mean they are at a dead tie at 150 yards and the 308 has a 200 ft lb advantage at 300 yards. Trajectory is within .2" at 300 yards, but the 308 has a 5" advantage at 350.
The 338 Fed can't come close to matching 30-06 at any range.
The 338 fed works. It kills stuff, but doesn't offer any advantage over 308 and won't equal 30-06. I understand why they didn't catch on.