I have the DVR XP. I core at about 450 to 650 and have it set to hard. Haven't had a problem coring 15" blanks. Keeping your knives sharp it key. If you didn't sharpen them when you got it you probably should have. Like Faust said you have to sharpen those knives such as the #3 after 1 or no more than two cores. #2 I can get 3 cores and #1 I can get 4 cores but no more than that for each one.