Great feedback! It's definitely true that I need to do some more research on this particular aspect. My trigger is set to 1 pound before it breaks (some folks set theirs to 2 oz!) Pulling it gently, like you're supposed to, shouldnt generate the same acceleration as if you were to "slap" it (which is a bad practice for accuracy and precision).

It may require faster data acquisition, so I hope that folks will contribute to the accelerometer project that I open-sourced to make that possible! https://github.com/ammolytics/experiments/tree/master/recoil...

Thanks again!

I'm not sure if you are correctly interpreting wrycoder's explanation. Or maybe I'm not, but I think his point is not about how fast the trigger is pulled, but about what happens as right after the trigger mechanism releases, independently of proper technique trigger finger technique.

Just before the trigger releases, you are pulling back with 1 lb of force on the trigger, and to maintain aim, are pushing forward with 1 lb of force on the butt (likely with your shoulder). When the trigger releases, suddenly there is no more force being applied by your trigger finger, but the same amount being applied by your shoulder. In response, the gun starts moving forward. It keeps moving until the trigger bottoms out and the force from your finger stops the forward progress, or until the recoil from the acceleration of the bullet begins.

I'm not sure he's right, but I think this is what he's saying, and I think it fits what you measured. I am confused though how the gun can move forward in the "preloaded" case. Isn't the gun already pushed forward as far as it can go against something incompressible? If so, how does it accelerate forward?

The easy way to control for this is to run the same measurements with a spent cartridge chambered.