Form my testing of this bullet from velocities from 2900 up to just shy of 3600 fps, I think its BC will finish out a bit higher then .900. If I had to guess right now with the numbers I am using in my 338 Allen Magnum with this bullet at 3500 fps which is a VERY mild load, its more like mid .900 range at least. In fact if I told you what BC I had to use for shooting at ranges from 1900 to 3000 yards many would simply call me a liar so I will not post that.
Ballistically, there is nothing that will run with them, YET!!!
My 375 Allen Magnum, with the right bullet should offer the same trajectory but I am predicting with 1000 ft/lbs more energy then the 338s will. All dependant on those bullet though but I know they will be coming soon. A certain bullet maker I know has a 375 AM on order already so I know he will be making the bullets!!!!
The 50 BMG is really a dog compared to these rounds. Only area it is superior is energy and thats it. But a precisely placed 338 bullet is plenty effective at any range.
This is the first bullet/cartridge/rifle combo I have tested that offered legit consistancy over 2700 yards which is the max I have found with the 300 gr SMK loaded to 3350 fps in the same rifle. In fact I have tested to slightly over 3000 yards and consistancy still seemed to be holding at that range as bullets were landing where they should be when conditions were read correctly. The rifle was holding around 1 moa at that range for the few groups I shot, I was very happy with that.
Back to the 375 version, other benefits it will have over these 338 monsters is more variaty of powder that will work very well, mainly more of the extreme powders that are not as sensitive to temp changes. Also, they will not be nearly as finicky or require the extreme barrel length. A 30" barrel should prove very capable of getting all you can out of the 375 Allen Magnum.
Also, big consideration, significantly increased bore life!!!! Recoil however will be increased as well but we can do things to control that!!!