I have a model 60 that my father bought me in the late 70's. It has a micro groove barrel common to all Marlin's of this era. I have shot many different brands and velocities. I have spent several dollars trying to find "the" round that works. It stands to reason that the standard velocity "target loads" shot very well on paper but were less than stellar on squirrels. I was at a loss. I had tried stingers, velocitors you name it I fed it to my 60. It was very interesting. My 60 hated high velocity ammo. Stingers made a shotgun like pattern with no rhyme or reason. Such was true of all high velocity loads. Hyper velocity? forgetaboutit. I finally found that CCI SGB's shot best groups on paper and were murder on squirrels. Thet are not hollow points, which as I was tought was the only thing to fire at game, they are a flat point. They work very well....I wonder what others have found about ammo and there 60's?