i didn't know the 597 was a shotgun...?
well on the bright side, i don't feel so bad about my shooting!
okay, okay, i'll be nice.
i would look into some different ammo. you should be pulling alot closer to MOA with that rifle and slow, precise shooting. for reference, there was a member here pulling off approx 1" groups at 30 yards with a 11.5" barreled 10/22 wearing a red-dot. maybe NINE? pitdogboy? heck, i don't know...
go and buy a box of every type of ammo you can get your hands on. go to the range with a pen,notebook and a caliper, then document the results. the barrel will need to get used to each ammo. 10 shots or so and then start shooting 5 shot groups.
some mid line ammo i've had good luck with is american eagle and mini-mags.
*edit*
what power is your scope? what are you using for bags/rests? nice rifle BTW!
*edit again*
here's the one i was talking about:
http://www.canadiangunnutz.com/forum/showthread.php?t=232446