Wait, there's 6 things that can kill a mob in one hit; Attack01, Attack02, Attack03, Smash, Windmill, Counter. Unless you want to replace each one with the Bolt Casting anim, then feel free.
How to replace:
1. Find your desired .ani with MabiUnpack, extract it somewhere (like a folder to keep everything organized)
2. Find the name of the other ani you wish to replace (In your case, rhand_a<somethingsomething>)
3. Rename your desired .ani to the .ani you found in step 2
4. Go to your Mabinogi folder (not the one in My Documents). If you have the folders all set up, skip 4a
4a. Make a "data" folder, inside that, make a "gfx" folder, inside that, make a "char" folder, inside that, make a "human" folder, inside that, make a "anim" folder, inside that, make a "tool" folder, inside that, make a "rhand_a" folder. In the end, it should look like
Mabinogi\data\gfx\char\human\anim\tool\rhand_a on your address bar
5. Put Step 3 .ani in this folder
6. Restart mabi
More info is here, my guide, I wrote it for a reason. Please look at it
Weapon Animation Translator