I shoot a 15" Bullberry 6.5 Super Bower at our clubs 500 yard varmint fun matches (2X4X6 blocks - shoot-offs on edge), and also in infrequent 1000 yard fun matches at another club (6' target, 10" bull). Shot prone with mechanical rests, bipods or bags legal. Off a Bower Rest, it at least equals the rifles and XP's at 500 (beats most of them - wins some of the time), and gives them a hell of a run at 1000. Have used everything from a 10X pistol to 36X rifle scope on this barrel.
It'll push 85's over 3000 fps, 100's to 2800, 120's to near 2700, and 140's near 2400 out of the short tubes, and there are some great bullets made in this caliber.
Just for S&G... in 1995, N.D. Mandan shot a 2 5/8" 9 shot group at 650 yards (IMR4350, 140 gr. Sierra @ 2290 fps) in a 3-5 MPH wind with a 14" 6.5SB pistol.
Shoot Center - Larry