How can I adjudicate more-lethal combat?

So, in FATE 2.0, characters take a lot of hits to remove from combat. This presents a problem when lethal weapons are used in situations where failure doesn’t make a whole lot of sense.

For example, when a character with “Long-Range Rifle Combat XXX” attempts to fire on a stationary generic mook from a concealed position after taking time to aim, their average MOS is going be 6 (three base +1 surprise +1 for taking time to aim +1 for specificity in skill). A MOS of 6 results in an ‘Injury’ outcome, one less than what’s needed to actually take the target out of the fight. The generic mook takes a -1 to everything until receiving treatment for their injury, but isn’t going to be surprised by additional fire in further exchanges, so the outcome is basically a wash when it comes to the expected result of futher combat. If the mook can’t do anything to get themselves into cover or in some other way interfere with the sniper they will probably be taken out after two additional rounds of combat. If the mook can get into cover or otherwise garner a +1 on their next opposed roll the combat will drag on for another 4 exchanges (we assume taking the time to aim to get the +1 needed to keep the average MOS at 5 takes one’s turn). This means that even with three points in a specialized combat skill a PC will routinely fail assassination attempts on completely vulnerable targets in ideal circumstances and that a Legendary result when attempting to effect “I shoot him right between the eyes” is either an abject failure or somehow consistently fails to remove targets from fights. That is not what I want.

This is additionally problematic when one is attempting to neutralize targets without being noticed, or when there are numerous opponents, or when the opponents have the capability to respond with potentially deadly force.

While changing a character’s overall hp is appropriate in some cases, that is not something I’ve had success in doing here, as I don’t want to have to figure out everyone’s hp boxes for every fight (as doing so would take away a significant portion of player predictive ability) and I do want a more usual HP breakdown in situations where prolonged combat is more reasonable.

What can I do to adjudicate highly-lethal maneuver attempts in combat in a more satisfying way?