This is the commercial version of the Harrington & Richardson, Inc. trainer (M65/165) for the M1 Garand that was used by the USMC during WWII.
This version, the H&R M151 Leatherneck, is chambered in .22 LR, utilizes blow back action that is based on the Reising submachine gun. It has a 22" heavy barrel, blued finish, 5 or 10 rouund detachable box mag, a Redfield M70 rear aperture sight with a ramped protected front blade sight, a walnut buttstock, and was manufactured only between 1948-1952 in Worcester, Massachusetts.
Keeping true to the military trainer, even though this rifle is the commercial variant, it weighs in at 7 1/4 lbs. The most unusual feature of this rifle is it's index finger plunger recessed in the stock for actuating. Enjoy....