Vigor

EDIT : this solution is outdated, the 1.1 Update resetted all medals and are now much easier to obtain with a more than forgiving time to get Gold medals!


Since this is one of the harder Achievements in the game, I found an interesting glitch that you can abuse to get Gold Medals in an insane fast amount of time.
(It should be noted that this Trick wont work with the scarecrow targets)
All you gotta do is complete a challenge, and during the screen fading Black scene walk backwards to get the challenge failed screen. Press A fast and you should still get the Screen for the completion as well and if you walk backwards while pressing A again you can chain it as long as you like. What this does is that it creates multiple plates or bottles at the same location so you can shoot them multiple times if you retry the Mission.
Remember the targets that are closest to you and with a good Portion of luck, since its not always a guaranteed duplication, you can complete the challenges in less than 6 seconds.
I highly recommend using this in plates- as well as bottle challenges.

This gets tricky, probably my least favorite achievement for the game and one of the worst I've ever gotten. as I mentioned in the achievement to win any firing range challenge, this will require a lot of skills and luck. I tried to shoot for challenges that gave me more than the lowest time limit to complete. The aim in this game is finicky and ballistic applies strictly. Some of the challenges require you to shoot 5 to 6 bottles in less Than 8 seconds try to bypass those.
It does not sound bad in paper but you'll understand what I'm talking about when you'll actually try it. But anyways, some automatic guns can be switched to single by pressing
And you can hold your breath by holding .
You can also switch from sight to shoulder aim with and in some challenges it is recommended.
Shoot for challenges that will take 10+ seconds to complete, plus look for bottles, plates and small road signs challenges, they are easier to hit and only require 1 bullet.
Mannequins and big road signs or distant challenges will require precise headshots / multiple shots and long range aim
And as I mentioned before but not undoables, patience, practice and a little bit of luck will help you out on this one.
If you're taking too long because you miss some "in sequence" shots, simply walk out of the box and it'll give you a failed challenge window, simply keep hitting try again.
Little trick : try to memorize a pattern that makes sense (from left to right, for example, and start with the hardest targets you can hit.
Start the challenge once and memorize the positions of the targets, then restart and start trying.
Note : some challenges will start you out with an empty magazine (shot gun one for example) so you have to reload in the first 5 seconds you have before the timer starts ticking.