You seem to be out on a limb on this one.;)
With a chrono and some messing around you can get there. After seeing someone else's experience with reduced loads of 4861 in a 243 I get a little queezy with the first shot but seemed to have survived so far.
I haven't messed with the 338 yet but will do so one of these times.
Here are some links:
Reduced Load Calculator
This could be a bit risky if double charged....
Blue Dot Loads
Here's my approach:
Hogdon lists IMR 4350 and the 250gr bullet data.
83 gr = 2820 FPS
78 gr = 2698 FPS
Thus 5gr pwdr reduction = 122 FPS velocity reduction.
Or about 24 FPS /grain of powder
Then 2968 - 2000 = 968 FPS desired velocity drop;
968 FPS/24FPS/gr = 40.3 grains of 4350 to get 2000 FPS.
As is the usual warning: Sneak DOWN on it a couple of grains at a time and stop "just before" something bad happens.
If nothing else, this response may well gather the attention of someone who really knows what they're doing and flame my little butt. But hey, I've been thinking about getting my butt 'waxed' any way.:eek:
PS: you may well come up with a real good squirrel load for that thing.