[Aethelwulf1972]

aside from the Shaprshooter quality, and a quality in assassin's primer, and just using enough take aim actions, are there any other methods of reducing the penalties for called shots? 

[Mittensworth]

Adept Centering will reduce any negative dice pool penalty for any physical or combat skill up to your initiate grade.  Note that this is a free action.  Also, doing a called shot is a free action, do you would need a way to have more than one free action in order to do both.

[ProfGast]

Martial arts techniques allow for the reduction in certain called shot penalties, up to a total of 2 off of the original penalty.

[Danny Montanny]

Heightened Concentration (Concern) from Shadow Spells is a must. Reduction of 1/2 Magic rating (round up) to Called Shot? Yes, please!

[ProfGast]

Heightened Concentration (Concern) from Shadow Spells is a must. Reduction of 1/2 Magic rating (round up) to Called Shot? Yes, please!

Even assuming that the adept power applies to Called shots, and I'm not entirely convinced it does, RAW has it "negating a single situational modifier of a value up to half your Magic Attribute" after using a Complex Action.

 That means unless you have other means to reduce your penalties, you still need Magic 7 and a complex action for the adept power to do you any good at all.

[Danny Montanny]

Called Shot is on a table titled "Situational Modifiers" and Heightened Concentration works for situational modifiers. Don't see how it would ever be confused.

With Strive for Perfection and Sharpshooter, even the hardest -10 Called Shots are dropped to -3, so just enough for Heightened Concentration and Magic 6 to take care of.

[ProfGast]

Hm the table IS defined.  Forgive me for not remembering that since SR5's track record with consistent nomenclature is… shaky at best.

Anyhow that means, assuming the GM is one who allows that quality combo, you've spent 16 karma and half a power point to allow you to take a penalty-less called shot over the course of two initiative passes.  Generally not worth it in my book outside of a sniper...

Though I suppose it works if you're also using Perfect Time and the Rapid Draw power as written, which could make for a comically amusing "brace of pistols" or "carries 6 sheathed swords" type of character.