At a later public trial held in 1722, a Puckle gun was able to fire 63 shots in seven minutes (approx 9 rounds per minute) in the midst of a driving rain storm.[1][7] A rate of 9 rounds per minute compared favourably to musketeers of the period, who could be expected to fire between 2 and 5 rounds per minute depending on the quality of the troops, with experienced troops expected to reliably manage 3 rounds a minute under fair conditions; it was however inferior in fire rate to earlier repeating weapons such as the Kalthoff repeater which fired up to six times faster. [Source: Wikipedia]

This is obviously a lower rate of rounds per minute than modern semi-automatic rifles are capable of, yet if the founding fathers knew of the existence of this technology, don't you think they could have foreseen the advancement to what we have now? They were, after all, a bunch of inventors.