I've had at least one .22-250 since the 70s. Bolt guns, all. From custom built to Winchester M70Varmint. Its a fine cartridge and does great work for what it is meant to be.
1-14" is the usual twist. 55gr and under, its fine. Back in the 70s, one maker did 1-12" eight others all did 1-14". This was the usual twist for nearly ALL .22 centerfires all the way back to the 20s.
Back when the heaviest bullets common were the Sierra 63gr semi spitzer and you were kind of odd if you shot those, it was the "deer bullet" where .22CF was legal for deer.
My current .22-250 is a Win M70Varmint. 1-14" twist. 55gr goes into an inch or sometimes 3/4" when I'm having a good day. 52-53gr match bullets do 3/4" to 1/2" when I'm having a good day. The 63gr Sierras go into 2 inches, or a bit less. Good enough for deer, a bit suboptimal for small varmints.
To get full performance, you need a long-ish barrel. More than 22" is better than less, and 24" or 26" gives you more of what the .22-250 is best at. Speed. Longer barrels allow higher speeds without as much need for "throat roasting" loads.
I would be interested in hearing first hand accounts of the AR in .22-250. Personally I think they would be a dissapointment and possibly a pain in the butt. Not the barrel accuracy or trigger, modern AR pattern rifles can be excellent in those aspects. What I'd be concerned more about is getting them to run reliably. Specifically under/over gassing the action. Also what barrel length? 20? 22? if those are your choices, you're giving up some velocity.
Additionally there is the whole matter of carrying around more rifle than needed. Doesn't matter for bench shooting, but if you're actually hunting, it does. Varmint barrel bolt gun with scope can go 12lbs what is an AR going to weigh without a varmint contour barrel??
Additionally, with a bolt action when you roast the throat, you can have the barrel pulled, set back, rechambered and reinstalled on your action. With an AR, you must replace the barrel assembly. Easier to do at home but you do need an entire new barrel assembly.
The .22-250 easily gives you 5-600fps more than the .223 and even more is possible if you push things. That, to me is a significant difference.
I load for .22 Hornet, .221 Fireball, .222 Rem, .223 Rem and .22-250, Varmint guns, light sporters or heavy varmint bolt action or single shots (other than .223 which I run in semi autos). Not benchrest guns.
.22-250 is king of the heap for me. The .220 Swift goes a little faster, at top end speeds, but the oddball case is it based on just turns me off. The .22-250 is the standard .473" head size which is just better for me.
If you want to shoot the ultra heavy (70gr+) .22 bullets now available, in a .22-250, get a barrel made with the twist that's right for them, not the usual 1-14 or 1-12. Good luck finding reloading data for them in that cartridge, though.
I think its a great round, but in an AR pattern rifle, I have my doubts...YMMV, good luck!