SGH,
I think we'll need a little more detail on this one to make any informed reply to your query.
How many figures were firing, at what range (long or effective for the muskets) etc.
A quick glance at the musket tables, assuming a British battalion of 30, which stays in the same bracket of figures, if at long range, would need to throw 11 or 12 for 3 turns running to guarantee taking a gun off the battery.
On the first turn the battalion would be on a -2 (+1 British in line; -3 deployed artillery), and on a -4 (+1 British; -3 deployed artillery, -2 fired last turn) for any subsequent turns, with any casualties halved for being at long range.
Any average throws by the battalion would have them killing 1 at best, and more likely have them throwing for half and quarter casualties.