Crosshair doubted himself when it came to firing the shot at Omega and Hemlock's cuffs. He was not willing to risk hurting Omega with a blast from his own weapon.
Crosshair, who at the start of the TBB arc in Clone Wars season 7 would have reveled in the complexity of his shooting skills, who could shoot a flea off Wrecker's back in the rain without hurting him, who was engineered to be the perfect sniper, was not willing to risk his blast being off and hurting someone he loves. Crosshair reached a point where, when it comes to his little sister, he wouldn't be cocky or arrogant. And besides, his shooting hand was gone. The hand that had caused him so many tremors but with which he'd also landed every shot he could be proud of...
And it was Hunter who encouraged him. Hunter, whose relationship with Crosshair faltered and strained and recovered, placed his full trust on Crosshair even when it came to Omega. Hunter, perhaps the only one who could rival Crosshair's concern for the kid, had no shadow of a doubt that his brother could make the shot without hurting her.
And so, Crosshair shot the binders perfectly, freeing Omega and allowing the three of them to destroy any threat to the clones, physically and metaphorically. Crosshair, Hunter, and Omega freed the clones, and they did it together.
They freed the clones through their love and trust in each other as a family, and I can't think of a more perfect, beautiful way for them to have done this. The clones are family. Loyalty means everything to the clones.