All the bottle caps you can receive during the challenges at the shooting range in Resident Evil 4 (2005).
There are 6 bottlecaps for each section, for a total of 24 caps from the challenges.
You can reach all game modes at once in 5-3.
After three bottlecaps (getting over 3000 points), the layout changes for the last two (technically 3, depending on the order in which you reach them).
In each game mode, the sixth cap is special: either you reach 4000 points OR you hit all the non-friendly targets somewhere on the body (you can miss as long as you hit them eventually, Salazar's head doesn't count towards the hit count though).
It's best to use the pistol for everything. The reason for not using the sniper is due to its shots piercing through multiple targets, so you don't get the 5 hits in a row for the Salazar head when you use it.