I made 7 balls on the break playing 9-ball when I was 13 years old.
The cue ball, 2, and 8 were the only balls left on the table.
I was playing a guy named Rob Perry on Wimpy Lassiter's old Gold Crown.
Most I've made since then is 5.
Short answer:
6 playing 9 ball many times; perhaps 7 but i'm not positive, just seems like I saw 7 years ago but thats not 100% certain(my best is 5), 7 with a full rack of 15(I did that and I am certain, I couldnt play a lick and thought that it was no bigdeal, thats just how pool was going to be, before that all I played on were messed up barboxs. This was on a 8' with 5" pockets table, in my mind a real table, so when i made the 7 I thought it was a difference in a good table from a bad table; a few days later I realized that I was very wrong and 7 wasnt a normal thing, funny how things look when you think back on them)
Long answer and something to read:
when I about 14 or 15 my dad got us a 8' table, I made 7 once myself playing 8-ball when I first got the table, like the 2nd or 3rd day I owned it. never did it again.
I saw 6 go in on a 9' gold Crown in a 9B tournament, but there was 2 balls going into the corner at the same time same speed and right at the opening (mouth) of the pocket. and knocked each other out at the last possible second, if one of the 2 balls was in front of the other 8 of 9 would have went in. This was at the Jointed Cue in Sacramento in 89? there was about 100 people in the tournament room. And saw this, He crushed the shit out of them, 3 or 4 went in instantly the others just rolled and all managed to find a pocket, "plop" in the the drop pockets. and the last 2 were comming up table-both at the exact angle and speed, I knew there was gonna be a collision, I have fast eyes for that(for what ever reason I dont know-I just do); I was hopeing that they would collide in the Jaws of the pocket, if they did they would have went in, because back then the pockets were a hair bigger 4 3/4"-4 7/8". So a crash inside the Jaws would have been enough.
On a Diamond table now days the balls might both get wedged in the pocket and not fall on a shot like that. I think we dont see 5-6 balls on 9 ball on the big tables go in as often nowadays because the pockets are smaller & less 9Ball & more 10 Ball, also the soft or cut break the plan is to make a ball get shape on the one and run out in 9 ball nowadays, like Donnie Mills does. So the guys like David Howard who crushed the balls 20 years ago has reworked his break into a more logical tactical shot to give himself a shot with shape on the one ball setting up a run out, like Donnie Mills does.
And with so much 10 ball now, its harder to make a ball on any triangle shaped rack, 3,6,10,15. If you hit the 2nd ball with 15 on deck 3 or 4 is possible on new cloth. My table breaks dry 50% of the time playing 8 ball-no matter who is playing, good breakers included(Shane is the exception, he pockets balls period)
Making 4 playing 6 ball is great, I did that once, and I have played LOTS of 6 ball or "Short rack" many years ago, It gave me a advantage, guys I couldnt beat playing 9 ball, I could playing short rack, because the break. My break is so bad, Its hard for me to break and run, I can run 9 and out easy or 8 and out better off someone elses break. Since in 6 ball 80%+ breaks are dryI felt like I had a advantage, I used to keep a log of all action and 6 ball was the best game for me.
the magic rack(which should have been invented 20 years ago-we had the technology, no one thought to cut a piece of film with a plotter) is amazing and I think we will see the number of balls made on the break increase at pro tournaments. The reason I say "Pro" is because they play on new cloth and for a magic rack to work all the balls have to be the same size, in most pool rooms the balls are worn to different sizes. At Pro events the balls are usually new, or new enough that they will rack correctly in a magic rack.
Best
Eric