EXCLUSIVE

Will Hayden -- the main gunsmith on the reality show "Sons of Guns" -- was arrested in Louisiana and booked for child molestation … but he says the arrest is the result of a bitter ex-girlfriend's false allegations.

TMZ has learned Hayden was arrested on Saturday by East Baton Rouge Sheriff's deputies -- and according to the Sheriff's website he is accused of molestation of a child and a crime against nature, an aggravated offense.

According to the Sheriff's website, Hayden was released Saturday after posting a $150,000 bond.

Hayden tells TMZ his ex-girlfriend, and mother to one of his daughters, went to cops more than a week ago and accused him of molesting their child. He claims the woman did it in retaliation for him ending their relationship.

Hayden also says the daughter -- who he is raising with his new wife -- was interviewed by Child Protective Services and returned to his home. He says he is fully cooperating with authorities.

Will's older daughter Stephanie tells us, "There was never any impropriety in our home. He was and is a good father."