People have been busted in New Jersey for having .22LR lever action rifles with tubular magazines that would hold more than ten .22 short rounds, violating their 10 round magazine limit.
Most semi-sane states that have magazine limits exempt rimfires with tubular magazines.
However, the firearm in your picture is a semi-auto, so it is by FrankenSTEIN and UpChuck's standards an assault weapon.
"2C:39-1y."Large capacity ammunition magazine" means a box, drum, tube or other container which is capable of holding more than 15 rounds of ammunition to be fed continuously and directly therefrom into a semi-automatic firearm.
The key though, is "semi automatic". If it was a lever action or bolt action rifle, it could hold >100 rounds and still would be legal. Oh, and just to make it interesting "NJS 2C:39-1w(3) "Assault Weapon" means a semi-automatic shotgun with either a magazine capacity exceeding six rounds, a pistol grip, or a folding stock."
So, depending, the NJ magazine limit can be 6 rounds, 15 rounds, or no limit at all. You almost need a law degree to own a gun in New Jersey!