How many shots can you get out of a 12 ounce paintball tank?
and do you have to have a regulator or can you directly connect it up to the gun?

Depending on the weight of pellet you use (under 8 gr), I would guess around 1,500 to 2,000 shots.

As long as you are using CO2 in the tank, you can direct connect without a regulator.

Regards;
Mike

how many shots can you get from a 20oz?
Then why would you ever need a regulator?

Really, the math is straight line.
If a 12 ounce gives you 1,500 to 2,000 shots.
20 OZ divided by 12 OZ gives you 1.7.
1.7 times 1,500 to 2,000 equals 2,500 to 3,300 shots in a 20 OZ.

I use a 24 OZ on a remote coiled setup and figure I get 4,000 shots using 7.0 gr pellets.

There is no reason to use a regulator with such a large CO2 capacity system.
You will get consistent shot after shot to the end of the bottle.