Each one of those would be treated as Powers, and depending on their "Rank" would either add a +1CS or +0CS to the invention's "Tech Rank" (phraseology from Machines of Doom) or Applicable Rank. Bear in mind also that there's a Cost/ Tech Cap of Monstrous at the beginning (before modifying things) for anything that could be realisitically produced using modern (real life) technology. The example they use is that of a Fighter Jet which can fly Shift X speeds only having a Monstrous applicable rank.
Armor Piercing is usually a question of the ammo, not the gun itself; Let's see... what kind of applicable Cost rank would AP shot have? That takes a bit of conversion, easily done. Handgun & Rifle AP shot is 5x more expensive than regular shot. That gives you something to work with. Figure out the firepower of the weapon in question, and use that as it's rank; multiply that by 5 for the "power" which the AP shot has, and you have the applicable cost rank of the AP shot.
Example: A standard Handgun does Ty(6) damage. 50 rounds of normal shot has a Fe(2) cost; 10 rounds of AP shot has the same cost. To
develop AP rounds at home, you's take the damage times the multiplier, (6x5=30), so you'd have an applicable rank of Remarkable to set up things to make your very own AP rounds. It's actually cheaper and easier just to buy the rounds off the shelf.
Scatter Shot affects everyone within the same area. The only examples I see off-hand for something capable of this sort of devastation are Flamethrowers, grenades, missiles, and Heavy Artillery. The
lowest applicable rank I see amongst these is RM (30). That's a good place to start.
Bursts can affect multiple adjacent targets with one shot, kind of the toned-down version of
Scatter. Comparing the Assault Rifle to the Automatic Rifle, I see that there's a difference of 5 for the burst-version of the weapon- and that's the lowest. going from 10 to 15
technically falls into the same category, but it's enough of a difference to warrant a +1CS in any case. But looking at the Handgun & the Machine Pistol, which also uses Bursts, the difference is more striking; Ty(6) bumped up to Ex(20). That's a +2CS which is probably more accurate in the long run.
Hope that helps somewhat...
