I would like to point out theirs a serous flaw in the Colonial Marine Tech book. In regards to troop transport, the railguns are obsoletly useless. It has to be a miss print. Calculating the actual force of impact, it does less than alot of 9mm that exist now, it could never damage a modern battle tank, nor any that existed at the time when the book was made, and going by the ships description of its armor, that its resistant to micrometors, micrometors, by calculations of the f.o.i., will project more energy than the railguns, and if its immune to those, or nearly, none of he diffrent railguns shell types would ever harm a marine ship, unless you shot it through a window, but considering the apc uses armored quartz as its window, i wouldn't count its windows as being week even if they ste a weak point.
Also if you look at the barrel width, the shells should be dramatically heavier, bigger, and cause greater damage on f.o.i. .