I recently bought a lever action Marlin 30-30 from the local dunhams here because it was on sale and I have always wanted this gun. I brought it home and started checking things over a little better (which I should've done at the store) and found that the magazine is very loose under the barrel, I tried tightening up the screw at the end and that didn't work. I was wondering if this is something that is supposed to happen with these rifles or if it's just faulty.
The muzzle end of the magazine tube is secured with what Marlin calls a magazine tube stud which is dovetailed into the barrel. If the dovetailed fitting is loose in the dovetail, the tube will feel loose. You may want to consider peening the two dovetail tabs just a bit to more tightly clamp the fitting. It should be pretty simple.
I would take it back but the sign at Dunhams says that there is a no return policy on firearms. It was a stupid pick up on my part I really should've looked it over better than what I did, also along with the magazine tube being shaky I took my scope off flipped up the rear sight and it was completely off line from front sight, it's ridiculous how off these two sights are.