Although it is possible that it is the ammo, I'd say probably not. You say you just got the rifle but it doesn't look new. did you buy it used? What do you know about the history of it? I wonder if the chamber has been damaged or was reamed incorrectly.
No matter what ammo you fire, it will fireform to the chamber. The chamber is supposed to have a slight taper from back to front to assist with extraction. if your chamber isn't tapered or if there is a wide spot near the shoulder, then your spent shells will become stuck.
Get a micrometer or good set of calipers and measure the diameter at several points along the length of the casing and compare to a new round.