Pete Campbell (Vincent Kartheiser) purchases a Marlin Model 25 in "Red in the Face" (1.07) with the $22 he received from returning a chip-and-dip he received as a wedding gift.
Daisy BB gun
Betty Draper (January Jones) fires a classic Daisy BB gun at her neighbor's pigeons in "Shoot" (1.09).
M1 Garand
During the Korean War flashback to 1950 in "Nixon vs. Kennedy" (1.12), Pvt. Dick Whitman (Jon Hamm) carries an M1 Garand before assuming the identity of his deceased lieutenant, Don Draper.
M1 Carbine
Whitman's lieutenant, Don Draper (whose identity he would later adopt after Draper's death in Korea), carries an M1 Carbine during the 1950 flashback in "Nixon vs. Kennedy" (1.12).