It's unfortunate that everything related to firearms is now viewed as political. There are just so many interesting things unique to thos subject matter that inquisitive and mechanically inclined people, like those on HN, are missing out on.

I'm just here to learn and share. Hopefully this will help towards breaking down some negative stereotypes about a fun an interesting hobby!

I suspect what you saw was the sudden release of the couple of pounds of rearward trigger pressure causing the gun to move forward shortly before the pressure buildup and recoil drove it backwards. That would swamp any small recoil associated with the firing pin.

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!

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?

1. Interference with the rifle barrel 2. Interference with the shell casing (is there a measure of how tight a shell fits the bullet that changes the velocity / is more interference fit good?) 3. do slight variations in diameter or weight matter more?

Great work!

It looks like youre measuring muzzle velocity with a device mounted to the barrel. If that's true, i suspect it almost entirely negates the difference you are looking for because the rifle recoiling adds perceived muzzle velocity that the target (and the rest of us) do not experience.

That said, I'm more interested in the truth than who is right or wrong. I've open sourced all of my data and want others to try this experiment for themselves and share their results rather than rely on me as a source-of-truth!