GLOUCESTERSHIRE'S Tim Hancock hit 135 to help his side to a Cheltenham & Gloucester Trophy record score of 401-7.
Hancock's superb innings was accompanied by 87 from Jonty Rhodes and 76 from Craig Spearman against Buckinghamshire.
James Averis then completed a 324-run win for Gloucestershire taking 6-23 as Bucks collapsed to 77 all-out.
Gloucestershire face Kent in the fourth round. The club were also celebrating the signing of New Zealand fast bowler Ian Butler as replacement for Ian Harvey, who is playing in the one-day series in the West Indies.
Gloucesterhshire's director of cricket said: "I am delighted to have Ian Butler join us for the final part of the month before Ian Harvey returns from the West Indies."
Elsewhere, Marcus Trescothick warmed up for a busy summer with England in fine style as he steered Somerset into the next round of the Cheltenham & Gloucester Trophy in Edinburgh.
Trescothick smashed an unbeaten 103 from just 70 balls as Somerset easily passed Scotland's total of 138-9.
Just two first class counties will miss out on the C&G Trophy fourth round after all potential banana skins were avoided.
Only Hampshire and Northamptonshire will have no involvement in the last 16 after defeats by Sussex and Middlesex respectively in the only all first-class third round ties.
Several county batsmen took the opportunity to inflate their averages against lesser opposition although Nottinghamshire were given a scare by Lincolnshire.
Sussex skipper Chris Adams led his side home in the last over at the Rose Bowl after Simon Katich's 82 not out had helped Hampshire to 213-7.
Adams hit an unbeaten 80 and shared in an unbroken match-winning stand of 54 with Mark Davis that saw Sussex win with three balls and four wickets to spare.
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