I've gotten some nice groups with my heavier boltguns, 308s with Rem Varmint barrels, and a heavy 30-06 with a Douglas #7 contour. Not 'all day long' though.

308 Win, 155 Scenar, 100 yards,
[Linked Image from i.imgur.com]

308 Win, 208 Amax, 100 yards, 10 shots, .65"
[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

Heavy 30-06, 190gr Sierra MK
[Linked Image from i.imgur.com]

Heavy 30-06, 210gr Berger, 3 shots, 100 yards. Wifey shot this in a postal match we were participating in.
[Linked Image from i.imgur.com]

Heavy 30-06, 208gr AMAX,
[Linked Image from i.imgur.com]

Heavy 30-06, 110gr VMax,
[Linked Image from i.imgur.com]

Heavy 30-06, 240gr Sierra MK,
[Linked Image from i.imgur.com]

The 308s,
[Linked Image from i.imgur.com]

The 30-06,
[Linked Image from i.imgur.com]