Of all the trigger dealies I've tried over the years, only the GAT crank worked even half-ass.
If you get the GAT positioned correctly, and really tightened down well so that it doesn't move on you, it works as advertised. It's even semi-usable if you have a bipod and set it up to crank with your off hand while holding and aiming the rifle normally with your dominant hand off the bipod.
Cranking and firing without a bipod or other support is fun, but not really aimable - bumping from the shoulder is better if you have to bump and can train yourself to do it.
