I had a Marlin until my son started hunting and decided he wanted it after taking his first deer with it. Mine needed jacket bullets, and was fine. Lead bullets shot a pattern not a group (think buckshot)unless I was shooting .38 spl wadcutters. Which incidently made a pop as they exited the barrel an no other noise. I think it had to do with the micro- groove rifling in them.

I recomend that you clean the barrel and make sure all lead is out of it which can be a pain. Then try jacketed bullets. My son's rifle likes Federal American Eagle 158 grain JSP's and Magtech's in the same style. It shoots better than we can hold it. Or about 1 1/2" at 100 yards. I did change the sights as the original bead front sight covered the black of a 25 yard pistol target at 100 yards. I put a plain thin post with a peep rear and removed the rear sight from the barrel.