Yes, The spread is pretty much a crapshoot, you lose most of your power at 0 and 11+ meters( due to a glitch for people getting too close for some reason, glitching inside your gun at 0 meters, 11+ is just the range you lose 2/3 of the power) or ping. Higher ping means you have to aim ahead of where they are, 100 or lower means you can shoot at them. regardless of ping, if they are running at you or jumped up from a lower location upto you, you can shoot at them still regardless of ping. But you might need to hopscotch back after your first shot sometimes.
In order for a spas 12 to 1 hit reliably, you need to bring an enemys armor down at a distance if possible. Many pointman make the big mistake of holding their ground when they can afford to fall back to take another shot, increasing that 1 shot kill on the next encounter, even with medic heals. Revolvers are pretty much instakill upto 25 meters with armor, 35meters without any armor points.
using the shotgun at a distance is ineffective at reducing HP, but does better at reducing AP, so if you have the chance, try to get in chip damage, every bit helps. Learning to aim higher than normal will help, the crosshair is significantly larger than any other weapon, so the idea of having the whole crosshair contained around the enemy will result in more shots tagging the body,and limbs and less on the head. have a crosshair with a center dot to know where the center is, that crosshair center should not go below the enemys head, it actualy should be slightly above for multipul reasons just for the pointman class.
I get that graphic that should have been a hs at 0-3 meters, but... thats how the game works, try to make ping limit rooms if possible.
You need so much effort to 1 shot kill with a spas 12, accuracy,damage, rate of fire is what holds it back, however you can fix the rate of fire issue by quickswitching, a skill used by snipers in any game with a long reload time. Also if you can take the accuracy mechanic of counterstrike and apply it to a pointman, you can be very fast, and still be fully accurate, i call it hopscotching, while using a shotgun. 3 shotguns are better to use if you are shieldshotting, Spas12, M870 and the Striker slightly, the 500 Tatical ( even permanent ) is not a great shieldshotgun, it's slightly better than stock, but barely, spas12 has better grouping while shielding at least, along with capacity.
if you can take advantage of the "hopscotch", you can make very frequent 1 hit kills reliably, as long as your on the higher ground or even leveled ground, hopscotching is harder with low ceilings and upward hills, you would want to hopscotch downhill or just on a leveled surface to keep mobility, accuracy and stability at max.
I could teach some of you guys who are interested in pointman how to use the weapons, how to properly use a shield and learn to be a team player, which is actualy a good thing to learn anyways.