The longest (and hence heaviest) bullet the rifle will stabilize depends on the twist rate of the barrel. Most 22-250's are 1-in-14" twist, which will stabilize bullets up to 55 grains. If it's 1-in-12" then it'd probably do ok with 62 grain bullets.

But it would be irresponsible for me to not caution you against using a .224cal rifle for deer, especially the larger northern deer. .224cal rifles are just not powerful enough to reliably make a clean kill on deer sized game, period. Don't let the velocity numbers lull you into believing that a 22-250, or any other .224cal rifle for that matter, is good for deer. Velocity isn't the only thing that factors into the killing power of a cartridge. Bullet construction is one, and there aren't too many bullets in .224cal designed for the type of penetration and controlled expansion necessary for large game. Another is the sectional density of the bullet, which determines how well it penetrates relative to other bullets. The SD of .224cal bullets, especially the 55grain and lighter, is pretty pitiful, and will not guarantee that the bullet will penetrate layers of bone and muscle to reach vital organs if your shot isn't absolutely perfect. Thirdly, even with 1.5-2x expansion without the bullet coming apart, that still leaves a very small hole. All this translates to zero margin of error for a shot against a deer.

Lastly, .224cal rifles nay very well be illegal for use on deer, as they are in most states and for good reason. If you have your heart set on hunting deer with your Encore, then go get yourself another barrel in .243Win or 6mm Rem. at a minimum. A couple other good rounds would be .308Win, or in pistol cartridges you could go with .44Mag, .480Ruger or .454Casull. All of which will do a very good job on deer at reasonable ranges.

But I'd admonish you to stay away from hunting deer with a .22cal rifle. Even though a .22-250 CAN kill a deer (and so can a .22LR, but that would clearly be ill advised, wouldn't you agree?), that doesn't mean that it's the right cartridge for the task. As responsible hunters it's our duty to select a cartridge that is capable of the terminal performance necessary to ensure a clean kill provided we do our part by placing the bullet in the kill zone. Any .224cal is NOT a cartridge that meets that standard.

Now if you were shooting at coyotes it'd be a different story!

Mike