Advise on keeping dog steady

[Lt1chevelle]

I have a 18month old BLM when working with him with the dummy launcher he goes nuts well with any gun shot noise he gets very alert. While just throwing marks with him at heel and also me 20-30 yards away he is very solid an won't brake, but as soon as I get the launcher out he wants to brake on me. What I have done now is put him back on lead with his pincher collar and keep him at heel while using the launcher and correcting him whenever he makes any slight move once the launcher is fired and will eventually switch over to choker/ecollar. Right now I'll take him out an fire off about 15-20 rounds some with a dummy that I allowing him to get if he stays still and some I don't allow him to get an I'll make him sit while I go pick the mark up them I'll also just dry fire an make him sit. Is there any other methods or ways you guys work your dog to practice steadiness? I'd love to hunt this year and not have to go and play dog trainer and keep him from braking while duck hunting
Thanks chris