> It really does mean that my poor accuracy with a large caliber handgun is from flinching.

When I shoot my revolver, I will load empty shells in a couple random spots, spin it, and close it. This immediately exposes any flinching or anticipating I'm doing. I squeeze the trigger, the gun moves slightly downward and no round is fired.

Do that a couple times and you learn to remain neutral pretty quick.

It's not as easy on a magazine-loaded pistol. I imagine you'd need to get some purpose-made dead rounds. And the randomization is harder.

Snap caps make great "dummy" rounds for these drills on semi-automatics.

https://en.wikipedia.org/wiki/Snap_cap

Randomize by loading a few mags with different patterns of blanks, and then shuffle the mags until you don't know which is which.

Blanks fire/have recoil. Dummy rounds exist that you can manually extract though.

Or have someone load them for you.

Thank you! Funny story: I built the accelerometer with the original intent to see if I could correlate "bad" shots during 600 yard matches to flinching. That's still a work in progress, but because I had it working I was able to use it for this experiment as well!

I live in Oregon and am fortunate enough to be within 40 miles of an amazing club where I can shoot out to 600 yards every week with an awesome group of people! For what it's worth, you can (and should) drive out to Ohio for the National Matches at Camp Perry in the summer. It's on your way to Cedar Point ;)

> "It really does mean that my poor accuracy with a large caliber handgun is from flinching."

It may also be how how you're pulling/squeezing the trigger. That's the problem I have, and consequently I am far more accurate with revolvers when using single action trigger pulls (hammer already cocked back, so the trigger pull is very short and crisp.)

> Wow, fascinating article.

Indeed. Outstanding work :)

> I'm a little surprised that the bullet has left the barrel before the rifle recoils, but I guess that makes sense with the differences in mass.

That puzzles me too. I mean, once the bullet has left the barrel, what force could be accelerating the rifle?

Two possibilities came to mind. One was ongoing gas expansion, but that seems unlikely, because the chamber pressure is small after 2.5 msec.

The other is something mechanical about the rifle. Could the barrel stretch, as the bullet is exiting? And then contract afterward? Or maybe some elasticity in the attachment of the barrel?

Thanks for the question! Keep in mind that a huge explosion (with 40,000 PSI) is happening inside the chamber of the gun. Some of that energy pushes the bullet forward and the rest pushes the gun backward. You're right though, the gases escaping the barrel also contribute to this, similar to a rocket engine!

Based on my understanding of the physics involved, it's entirely possible that the rifle has accelerated to the recoil velocity by the time the bullet leaves the barrel, yet not actually moved measurably yet.

Well, but he says that he's measuring acceleration, not velocity. The bullet's in the barrel for just ~2 msec, and there's appreciable acceleration -- not just movement -- for >50 msec. It's true that his custom accelerometer only records data at ~6 msec intervals, but I don't see how that could smear ~2 msec out to >50 msec. Unless maybe there's some design limitations of the sensors that he used.

The PRB covers the role of propellant gases in recoil, and measures effectiveness of muzzle brakes.[0] He talks about 20%-50% reduction in recoil with muzzle brakes. And that implies that gas expansion from the muzzle accounts for at least 50% of recoil.

Even so, some additional measurements might be useful. It'd be interesting to know, at sub-msec sampling rates, the velocity of gas leaving the muzzle. And if there's still appreciable unexplained recoil: 1) the length of the barrel; 2) the displacement of the barrel from the stock; and 3) the diameter of the barrel, measured at maybe 4-5 points from the chamber to the muzzle.

Because steel is, after all, notoriously elastic. And the barrel may be attached to the stock in a way that smears out recoil. Also, the rifle may have other recoil-management features that reduce recoil, and smear it out. It's bolt-action, so there's no blowback, and I don't see a muzzle brake, but ???

0) http://precisionrifleblog.com/2015/07/01/muzzle-brakes-recoi...

The barrel and the entire gun must stretch and flex while firing. That flex will store some acceleration.

Also consider that multiple bits of the gun are mechanically attached to each other. It looks like the accelerometer is attached to the barrel, whereas the majority of the rearward forces before bullet leaves the barrel is acting on the bolt. Even as a bolt action, there's plently of interesting mechanical interfaces to absorb energy and movement before transferring to the barrel.

Thanks. In the PRB post that I cited, it's noted that recoil force can be "in excess of 1,000 pounds", but that "the recoil event is very short, lasting only about 10 milliseconds". So yes, I suspect that the gun is absorbing most of that elastically, and then relaxing on a longer timescale.

0) http://precisionrifleblog.com/2015/07/01/muzzle-brakes-recoi...

The interesting thing is that powder particles will leave the barrel before the bullet does. My guess is they have enough energy to squirt around the bullet before the rifling can deform it and create a seal.

https://www.youtube.com/watch?v=BPwdlEgLn5Q

> I'm a little surprised that the bullet has left the barrel before the rifle recoils

Well not 100%.

That's why it's important to hold a rifle in a position where it will kick back in a straight trajectory.

There’s a 1000 yrd rifle range in Wolcottville, IN (near Elkhart). Young’s Long Shot Range.

In Ann Arbor we have a range outside of town that lets you shoot out to 600 yards.