I'm using CCI Mini Mini Mag 40gr. for breaking-in my new Remington 597 .22LR & have only put 104 rounds through it & so far haven't had any issues with the ammo. Some say the cheap ammo won't work well with the 597s, even with Remington ammo. I've read really good stuff about CCI ammo in the 597s(and CCI overall in any gun) so thats what I went with but like others said already it is a little more pricey than some but makes up for it in performance.