Yeti,
Unfortunately, the .22-250 pistol velocities in comparison to .223 rifle velocties, is about correct. You're going to loose roughly, 200-300 feet per second going from a 22-24" barrel, on down to the 15". Usually about 28-35fps per inch.
It also depends on the burning rate of the powder you're using as well.
If you're looking for .22-250 rifle like energies in a 15" Encore barrel, try going the .243 route.
A 55-75gr. VMax load in that length barrel will net you velocities/energies that are "on par" with the 250's in a rifle. Possibly higher because of the slightly higher BC of the .243 bullet.
Right now, in my 15" Encore, I'm using a 55gr Sierra BlitzKing over 43.0grs. of Varget, with a Federal 210Match primer. The velocity is running about 3650fps. and the load is still a grain and a half (or two) below maximum.
Book loads for a rifle in .243 run at 4000fps for 45grs. of Varget, so go figure.
I've got a Savage Striker in 7mm08, and it's a beauty for an "all around" deer & coyote gun for sure, but if deer season was over, I'd be toting the .243 because it seems to have much more punch on them with the lighter bullets.
Honestly either caliber, loaded right, would do just fine for either deer or coyotes. The bullet choices in the .243 might be better overall, because the lighter bullets would be more preferred for coyotes (at least by me), but there's still adequate "heavier weights" for taking deer.
The lightest bullets for the 7mm08 run around 100grs on up, in weight, and the load I'm using now is a 120 Nosler BT, also with 43.0grs. of Varget at only 2630fps. give or take.
Although it would take a coyote cleanly I believe, again, I like the smaller faster, more frangible bullets that the .243 offers more so. It seems like it just drops them faster.
FWIW.....
Take care,
Bob