Not really. If you headshot someone by afar unless sniper you're most likely to survive it.
E.g. G36E headshots you from like across the map but not in small maps.
Btw, when pistolling, I shot at nuts and it did a lot of damage up close and it's not one hit kill because I was playing with myself (Computer & laptop) with the public aimbot.
K5SD is one of the best choices you could make. I have it perm, and working on my 64 day USP Tactical SE to get perm, but i need more renewal kits. They work incredibly well when used together in a match. Run out of ammo for your awesome usp tactical se? No problem, whip out your K5SD and kick their asses.