This table is, indeed, calculated by assuming that a ship can produce constant acceleration away from its origin, instantaneously pivot \$180^\circ\$ at the midpoint of its journey, and constantly decelerate for the second half of its journey. The greatest veloticy thus attained (w.r.t. origin) in the table above is roughly 1 million m/s--approximately 1/3 of one percent of c--so we're comfortable sticking with classical calculations.
The formula that produces the above times is:
$$ t = 2 \times \sqrt{\dfrac d a} $$
where \$t\$ is measured in seconds, \$d\$ in meters, and \$a\$ in meters/seconds2. (G is rounded to 10 m/s2 for ease of calculation. Note that the table gives distances in km, so you've got to tack on three zeroes to end up in meters.)
Those who would like a refresher on their classical kinematics, read on:
Recall that the distance travelled when starting at rest and undertaking constant acceleration is given by
$$ d= \frac 1 2 at^2 $$
Solving for t gives us
$$ t=\sqrt{2 \times \frac d a} $$
In our situation we consider the time (t1/2) to accelerate to the midpoint of the journey (d1/2):
$$ t_{\frac 1 2}=\sqrt{\dfrac{2 \times d_{\frac 1 2}}{a}} = \sqrt{\dfrac d a} $$
Doubling this gives a total trip time of
$$ t=2 \times \sqrt{\frac d a} $$
On page 75 of my "Traveller_2e_Core_Rulebook.pdf", I have:
Bulky: A Bulky weapon has a powerful recoil or is simply extremely heavy – this makes it difficult to use effectively in combat by someone of a weak physical stature. A Traveller using a Bulky weapon must have STR 9 or higher to use it without penalty. Otherwise, all attack rolls will have a negative DM equal to the difference between their STR DM and +1.
This page also lists a "Very Bulky" trait, which requires STR 12 to use effectively.
Best Answer
In Mongoose traveller (v1) there is a small paragraph detailing how piracy works in that version.
You can also have them lurking around gas giants to hit freighters scooping up unrefined fuel to save money.
Another option is a planet or set of planets with very low law levels where there is no protection from authorities. But then you as referee would have to come up with a good enough reason why anyone would come to such a dangerous area.