As it stands, Atomic Fire's main point is to charge it up to maximum, build pressure on players and unleash a OHKO on their faces. Powerful weapons such as Astro Crush and Hard Knuckle have their drawbacks, such as standing still and suffering knockback respectively. In the case of Atomic Fire, all you need to do is get away, charge it up then look for a victim. From a Deathmatch perspective, it depends on the map. Like say, a map such as MM1CUT has an overall small layout so the risk of players getting too far ahead of you in frags or getting killed before you even charge up to two levels is a lot higher. However, in MM5DAR it's a pretty damn good strategy to charge it up when it's less crowded, then look for victims. The fact that it can rip means that if it's shot down a crowded hallway, it could mean more than one ezpz kill. Whether they land said shot or not, players can potentially continue along their merry way and charge up another shot to try and score a strike down the alley again.
While this has been Atomic Fire since v1a, and I'm used to the way it works, I have to agree that it's not practical. Therefore, I have a couple of suggestions. The idea is to keep the "build pressure, unleash huge damage" theme the weapon has going, but looking at it from a different perspective.
A.
Damaging Afterimages - when Atomic lvl3 is shot, it is a one-hit projectile whose impact does pretty high damage but doesn't OHKO. However, the afterimages that trail behind said shot can "rip" a bit farther (maybe 128 - 192 units?) after the projectile has hit, causing damage akin to Laser Buster but much less damaging. With this method, you can still OHKO a player if the shot and most of the afterimages connect, and potentially get others damaged with the afterimages. As a bonus, these Atomic afterimages could rip through walls to give the weapon more utility, but this isn't really needed.
B.
Distance Power Decrease - when Atomic lvl3 is shot, it works as it does now. However, at mid-range, it becomes a lvl2 shot. At long range, it continues on as a lvl1 shot. You can still get OHKOs on players, but you need to earn it by getting
somewhat close or with prediction around corners. No need to fear a stray lvl3 shot anymore, though. If you hear Atomic Fire being charged at maximum, chances are you're within OHKO range.
As for weapons to discuss next, please let it be Noise Crush. I already made a suggestion about it
here.