Bullet Stability Logic 

Mark’s understanding of projectile physics is truly remarkable. Thanks for making these concepts easily digestible.

A couple of years ago I was at a match shooting 223 out to 300 meters. An 80 year old contestant asked me what bullets I was using, I told him Hornady .224 52GR BTHP. His comment was, they are too light for the weather conditions, (it was hot and there was a mirage) he told me that I would get vertical stringing, he was right.

This has got to be the most explicit teaching available on the Internet on this subject. Very, very good! Thank you!

Congratulations Mark, you've rendered a difficult topic into its component physics with the fewest clearest words, well done!

Best video I've seen about this subject. Thanks for sharing this info.

Excellent and informative as always. Thanks Mark .

Great stuff Mark, I love the technical aspects of the art. Thanks!

Brilliant explanation. Thanks very much Mark.

Mark, that’s fascinating and a great, easy to understand explanation. Never seen “transonic zone” addressed like that. Thanks!

Hyper-Stabilized Rifle bullets by James A Boatright. (and some of his other papers). If all goes well this fall I hope to be testing some Warner Tools Flatline bullets, 198 gr with and without the Tubb ring, in a custom 300 Win Mag, 33" PacNor barrel, 1 in 6 twist, 3 lands and grooves. I would also like to try Erik Cortina's dimple in the base of the bullet, but one thing at a time. Thank you for the videos, even after 7 decades, I enjoy learning something new.

Great explanation. Different tools for different applications. Not better. Not worse. Just a keen understanding of the various nuances and related aspects of the subject. Bravo Mark.

Always excellent videos. I learn something every time. Thank you

thnx for explaining a big problem in a simple way

Thank you so much for the great information. Really enjoy your channel and your incredible marksmanship.

My browning highwall in 45-70 has won competitions at 1,600 yards with its 1 in 18 twist barrel with paper patched lead bullets and black powder. It’s amazing what older technology can accomplish when you really get down to brass tacks and nitpick every detail.

Great information, as always. Thanks.

You make it easy to understand. Great job once again.

Very informative. Thanks Mark 👍

Nicely explained, thank you!

Very good information! Thanks

Very educational as always, thank you.

Great video explaining this. The science behind this is so interesting.

As always, great stuff!

Best explanation of the details. Thank you sir, this will be a video I'll share with friends who understand physics and love to understand better what is going on with bullets. The back end wanting to go forward is something we actually discussed before.

Best explanation I've found of bullet stability & transonic effects.

Um exemplo excelente tem a natureza, uma 💧 melhor dinâmica!

Really enjoyed this video, very informative 👍

Fabulous explanation.

Great content thanks for sharing

Awesome information as usual

Another great video, Mark. Apologies I haven't had a chance to watch and comment for quite a while. Trying to keep up with......everything. Really enjoyed your bullet stability video. I always tried to explain it by talking about a perfectly thrown spriral from a seasoned quarterback, but these were great. Hope all is well? Be safe!!

Thank you for another great video.

Excellent information. Thank you!

Thank you for the knowledge

Fantastic presentation

A very interesting topic , good explanation

Great content.👍👍 A great comparison is the 244 Remington 1in12 twist and a 26 in barrel the 6mm Remington. 1in9 twist and a 24 in barrel Remington changed so it could stabilize the new spitzer bullets . Keep up with the great information.👍👍

You had me when you said center of pressure and I knew you knew what you were talking about.

Interesting topic Mark. You already brought it up with the dart, but I couldn't help but think it's a related aerodynamic problem to rockets or aircraft. To be stable, they also need their center of lift to be behind their center of mass (or CG).

Thanks for the info!!

I have a Howa .308 24in 1/10 using 155gn and have shot out to 900 no probs. We have electronic targets at the club so they haven't reached the transonic zone yet. I'll be shooting 1000 in a few weeks so I'll know then.

I had no idea a bullet had that many revs on it.

You can think of foster style shotgun slug as a shuttlecock of lead. Heavy in the front and a hollow base keeps a nose forward orientation without spin.

👍😊 compromise so a 1:11 22” barrel 308 is that. It’s good with the 168 bthp and trash with 150ish fmj .

ahhr yes understanding more now cheers. ok thinking out loud why not drill a micro bit out from the rear of the projectile to shift center of gravity forward a little as such.

My .300 win mag has a 26 inch barrel with a 1:10 twist rate. Fairly standard I think, but am really not sure. It's really hard to understand what happens at extreme ranges, as we can't see much. Lots of trial and error to get things dialed in. It would be interesting to capture a bullet in a ballistic gel block out past a mile or so, and see what the impact looks like. Would be a hell of a shot that's for sure! Thanks for sharing, cheers!

I think the "transonic zone problem" is rarely a problem and people seem to confuse it with stability problem some bullets experience in "subsonic zone" (jaw of repose increases- drag increases etc). Strange, but even zero jaw drag coefficient of many flat base SP riffle bullets isn't less than typical 9 mm FMJ bullet in subsonic zone...

I've often wondered if projectiles can be made with weight foreword of centre. by making the back less heavy.

Thanks for the explanation. What do you make of the 8.6 blackout's 1 in 3 twist?

So, the ultimate long range bullet would have a copper jacket, and the front "half" of the core made of lead. with the rear part made of aluminum... maybe someone will make them someday :)

So bullets with lead in the nose area and copper in the rear would be more stable possibly, while keeping the twist rate not so fast. So we could be shooting those 131g 0.257 bullets in a 1:10 twist barrels if the bullets were made correctly. My worse encounter was with the Barnes 168g LRX in 7mm with a 1:9.25 twist barrel. they hit the target sideways at 100yds. They have a recommended twist of 1:8, but even when we tried them in a 1:8 twist barrel they still weren't stable. I suspect that rifle doesn't have a 1:8 twist barrel even though Browning says it does.

Great explanation, thank you. I've built carbon fiber rockets from 1" diameter up that break the sound barrier. The centre of pressure vs centre of gravity is what makes them stable, if you get it right. So I understand your expectations. Yesterday I brought a Howa 22-250 and was a bit perplexed as to why their 223 has a 1 in 8" twist vs the 22-250's 1 in 12" twist. Does anyone have an explanation for these choices of twist rate?

Are there any good computer programs to design and test bullet profiles?

Have you ever tried the 240 grain Woodleigh bullet in a 1 in 10 twist 30-06? Kind of wondering if it would stabilize.

Gday Mark and Sam. Another very informative upload. Do you think barrel length plays in to stability and developing an effective RPM as well? I have a nice tikka 223rem that can shoot 1/4” groups at a 100m with lighter projectiles -50gr and 53gr hornady vmax. I have been struggling to get an effective load for the heavier 75gr hornady ELD match however. Groups at a 100m have been terrible. 2.5”! But still seems to be cutting clean round holes in paper. The rifle is a 1 in 8 twist (checked) and is 22.4” barrel length. I’d love to get this load to work for some long range target shooting (600 - 800m). Cheers 😊

Hi Mark. Just wondering if you've see Eric Cortina's video where he chucks his bullets in a lathe and bores a hole in the back with a centering bit. I'm not sure if it's a piss take or whatever but if it legitimate and doesn't cause other issues maybe you could try it to help balance those sgk's. Just a thought.

✌️👍‼️

Thanks Mark, Have you tried 230gr A max bullets in a 10 twist 300wm by any chance? I am just starting to work them up and they seem fine at 100 yards, 2834fps. Am I wasting my time trying to take them to a mile? Hornady says 9 twist minimum

👍👍👍👍

Too much spin isn't really a problem as long as bullet doesn't get deformed

Why don't people make bullets with a long tail, i.e. shaped more like a teardrop?

Mark, by my math, a bullet travelling 3,200 fps with a 1 in 7 twist rate will leave the barrel at 27,428 rpm's. Apologies to nitpick, and extra apologies if I am in error. I love what you do and how you present it. Respect.

i think this was what the internet was invented for/

The stability of a bullet in flight is determined by its angular velocity and the moment of inertia around its longitudinal axis. Angular velocity is the rate of change of angular displacement, and moment of inertia is a measure of an object's resistance to rotational motion. When a bullet is fired, the rifling inside the barrel imparts an angular velocity to it, which affects its stability in flight. The angular velocity of a bullet is proportional to the rifling twist rate and the muzzle velocity of the projectile. Specifically, the angular velocity is given by: w = 2πNT/V where w is the angular velocity, N is the rifling twist rate (in revolutions per unit of length), T is the time the bullet spends in the barrel, and V is the muzzle velocity of the projectile. The moment of inertia of a bullet is determined by its mass distribution and shape. The moment of inertia around the longitudinal axis of the bullet is given by: I = (1/12)M(L^2 + D^2) where I is the moment of inertia, M is the mass of the bullet, L is the length of the bullet, and D is the diameter of the bullet. The stability of a bullet is determined by the product of its angular velocity and moment of inertia, known as the spin-stabilization factor. The spin-stabilization factor is given by: S = wI When the spin-stabilization factor is high, the bullet is more stable in flight and less likely to deviate from its intended path. However, as I mentioned earlier, there is a point of diminishing returns where additional rotational energy doesn't significantly enhance stability and can introduce aerodynamic instabilities. So, in summary, the stability of a bullet in flight is determined by its angular velocity and moment of inertia around its longitudinal axis. The optimal angular velocity for a particular projectile is determined by the rifling twist rate and muzzle velocity, while the moment of inertia is determined by the mass distribution and shape of the bullet. The stability of the bullet is then determined by the product of the angular velocity and moment of inertia, known as the spin-stabilization factor.

Mark, you are using logic again. That is not acceptable in this twisted world. Be careful, mate, you might get "cancelled", but not by me.