45/70fan -
CCI Mini-mags and CCI SGBs shoot great in mine. However a lot of other ammo from Remington, Winchester, PMC, RWS, Federal, etc. etc. prints the worst groups I've ever seen in a rimfire rifle. I'm talking 3" groups at 25 yards from a rest with decent scopes. Until I found success with CCI ammo, I was convinced this gun was a giant piece of crap (excuse my French). Other 597 owners report this gun is finicky, but once you find the right fodder it more than holds its own.
Volquartsen has a replacement hammer that cuts trigger pull in half. Check out their website for a picture. The cut-out holes are different from stock hammers.