John Jacobs and Jim Ahern share fourth place at eight-under par.
Snead broke the old mark of 65 set here last year by Bruce Fleisher and 2001 champion Allen Doyle. The 64 matched the tournament record for 18 holes which was set by Jose Maria Canizares during the first round of the 2000 event, which was held at Hobbit's Glen Golf Club.
'I didn't play that much better today than yesterday except for making eagle at No. 12 and holing the bunker shot at No. 18,' said Snead, who opened with a three-under 69 on Thursday.
Snead flew out of the gate Saturday with four birdies in a row, starting at No. 1. He ran home a 15-foot par save at the ninth to make the turn in four- under 32.
The 61-year-old started strongly on the back nine with a birdie at the par- three 11th. He then holed an eight-iron from 133 yards at the 398-yard 12th for eagle.
Snead dropped a shot at the 15th hole when he landed in a bunker and failed to get up and down. He reached the par-five 16th green in two and two-putted for birdie. When he holed a blast from a bunker at 18, he assumed the top spot on the leaderboard at 11-under par.
'That was fun today,' said Snead, whose 64 was his lowest score since a 63 in the final round of the 1997 Comfort Classic. 'I kept the ball in play all day. I got off to a good start with the 15-foot birdie on No. 1 and then three straight after that. The good save for par at No. 9 kept things going.'
Snead had not held a piece of the lead after 36 holes since he was alone on top at the 1996 Vantage Championship. He went on to finish fifth in that tournament. His last victory came at the 1995 Senior Players Championship.
Davis, a co-leader after the first round, collected three front-nine birdies but ran into trouble with his flat stick around the turn. He three-putted from 15 feet at the 11th for a bogey and missed a four-footer for birdie at the next hole.
Davis sank a 10-foot birdie at the 14th hole. A tap-in birdie at the 16th gave him a round of four-under 68 and a share of the lead.
'If anything, it's a little disappointing,' said Davis, who finished third at the Farmers Charity Classic at the end of May. 'I missed some short putts but all in all I hit the ball solid again.'
Fleisher (70), Bobby Walzel (69) and Doug Tewell (69) finished tied for sixth at seven-under-par 137.
Doyle shot a second-round 69 and was tied for 15th place at minus-five.
Full field scores from the Greater Baltimore Classic