To give a little of my background knowledge.
In dark heresy 1e 40k roleplaying game the two snipers available from the start were longlas and hunting rifle (basically a weaker longrifle). It very quickly became meta for players to put the hotshot charge pack on the longlas or the dumdums on the hunting rifle. (i personally prefer lathe bodyblowers). Then at some later stage i remember hearing that in maybe OW (a later game) that the longlas comes with and is exclusively used with a hotshot charge pack. So in other words jawripper is correct.
The reason for the st4 of the longlas is because it already has a hotshot. However why -1 ap disappeared i dont know, and why it was replaced with 2+ ammo roll is anyones guess. But i think these were mostly used to differentiate the two rifles longlas and longrifle to stop overlap. Strangely it has usually been the case in 40krp that solid projectile weapons like the hunting rifle will out range the longlas. This was explained as being due to the laser losing coherency or focus at long range or something... a solid bullet only has the problem of air friction and gravity, something that a laser beam doesnt have to deal with.
So, in conclusion:
I can almost tolerate the loss of -1ap at a long range like 36" but i however do believe that the longlas should have an accuracy bonus in short range, just like the comparison between lasgun and autogun. This would serve to further differentiate the two sniping rifles and i dont think it would detract anything from the game nore would it overpower any side because everyone treats the longlas as common.
So yes, the longlas remains exactly the same as it is in the rulebook, hotshot cannot be applied twice bc you are not a techpriest (and should probably buy a lascannon anyway), however i'd give it +1BS at 18" and -0BS at over 18".