You're probably thinking of the Remington Nylon 66. It is very real, and it does shoot. It's a .22 LR semi automatic rifle. A couple variations were made, including variants which feed by a detachable box magazine, and variants which feed by a tubular magazine which is inserted through the rear of the buttstock.
Shoot - advertising magazine - was created in 1960.
You need to contact Remington for a correct answer.
Put in the magazine. load the magazine, and shoot.
Depends on what it is choked.