I recently got a mini 580 series with 1 in 9 twist. Consistently hit 3-4" groups off a bag with Simmons 3-9 scope. After reading thhese forums, decided to try the easy first. Bullets, - best results were 69 gr hpbt, added muzzle break welded to front sight, and made a new gas port bushing with a .042" hole. Now dropping brass about 10', and consistently holding 1.5" to 1.25" groups at 100yd.