Those Marlin bolt actions were surprisingly accurate for their price point. Only gun I've ever had stolen was a Marlin 22 mag I got as a graduation present. Off the top of my head, I own four rifles and two pistols in the caliber. Both pistols and one rifle are switchable cylinder revolvers that will shot both 22 mag or 22 lr depending on cylinder installed (one pistol I don't own a 22 lr cylinder for). There isn't much for target or benchrest style guns made in 22 mag, unlike the long rifle, so yes you can find more accurate 22 lr guns out there. But for just your run of the mill, walking around style guns, the 22 magnums seem to be every bit as accurate as the 22 long rifles, if not more so. They do have issues making them function reliably in semi-autos. I would steer clear of most semi-auto 22 magnums. I do own a Magnum Research 10/22 clone in 22 magnum with a carbon fiber bull barrel. Nice light gun and extremely reliable, I can not remember a single failure in a few thousand rounds. Never got the accuracy I wanted out of it though, 1 1/2 inches at a hundred yards is about all I have been able to get out of it.
The 22 magnum is an absolutely deadly gun on game, in the field it performs all out of proportion to what the ballistics are on paper. I wouldn't hesitate to shoot anything in North America with it (with proper ammo, of course). A hundred yards or a little better is about what I would be comfortable using it for on coyotes, not that it won't kill them farther, but it starts to drop and wind starts to effect it past there quite a bit, you would need to know your drop and have time to range the coyote and adjust, and hold for wind. Coyotes often don't give you that kind of time.
Where a 22 lr outshines it is in ammo prices and availability, and in a pistol the magnum is an ear breaker.
And yeah, I would say the magnum is overkill and would rough on squirrels for the table.
