I fooled with several AR-7s over the years, from an original Armalite when the design was new to a later Charter Arms, and a friends recent Henry. The design is a GIMMICK for people who have been reading too much pulp fiction. The zero wanders, accuracy is inferior to a target grade autopistol or field grade bolt rifle in this caliber, and the gun is difficult to shoot well.
Agree that the Marlin Papose and take-down Ruger 10/.22 are probably the best backpack .22s out there in current production.
If you search pawn shops and yard sales you can find simple, takedown .22 bolt-actions which work well. I have an old Remington pump gallery special which was originally a .22 short, but which I had John Taylor reline and put a good Bentz chamber in .22 LR and rework to feed .22 LR reliably. It has very rugged fixed open sights which are zeroed an inch high at 25 yards and it drives a ragged hole with CCI Subsonic HP. I did not scope the rifle because I was interested in simple, rugged durability for pack carry in areas where I cannot legally take a handgun.
Another good choice if you can find one is the Browning .22 autoloader. This is a compact take-down semi-auto rifle which feeds from a tube magazine through the butt. Sights are mounted on the barrel so that zero repeats when stowed apart and reassembled. You can store the rifle with chamber empty and tube loaded, and rapidly assemble and put it into action. These are about as accurate as the 10/.22
If buying a new gun the take-down Ruger or Marlin Papoose ARE the way to go, I just point out these others because you should not turn down a chance to buy a serviceable older gun if you come across one.