Usopp is a idiot! [Minor spoilers]

[Trafalgar Law]

Originally Posted by Sigart

Tim-Tim's right. I don't remember when exactly he says it, but he does use dial's on Kabuto. If I remember correctly he can also use a flame dial for his firebird. Also he gave some of the dials to Nami for her climatact.

As for using them in close combat; he very simply doesn't have the strength to do it, even if he did collect the courage. If you noticed when he used it against Luffy, he was almost sent flying himself from the recoil. It was also shown in the filler at the end of the 4th season (Navarone) when they were trying to get out, he needed teh support from both Sanji and Zoro to handle the recoil, even though he wasn't injured.

Its not really recoil, Its just a double-edged sword. The impact impacts you and the opponent.

[BlazeCommanderASCE]

Originally Posted by Trafalgar Law

Its not really recoil, Its just a double-edged sword. The impact impacts you and the opponent.

Yep, but the side facing the foe does more strain