DESTABILIZATION
- Thread starter HartBurn
- Start date
There isn't a specific distance valid for all rimfire projectiles at which stabilization is lost. The same can be said for .22LR projectiles. There are too many variables.
A google search that anyone can repeat shows that gyroscopic stability can be calculated using the formula below.
Sg=8πρairt2d5CMαA2B𝑆𝑔=8𝜋𝜌𝑎𝑖𝑟𝑡2𝑑5𝐶𝑀𝛼𝐴2𝐵
The variables are as follows:
| Sg𝑆𝑔 | The gyroscopic stability factor. A bullet is stable if Sg𝑆𝑔 is over 1.0. |
| ρair𝜌𝑎𝑖𝑟 | Air density |
| t𝑡 | rifling twist |
| d𝑑 | the bullet's caliber |
| CMα𝐶𝑀𝛼 | the bullet's overturning moment coefficient |
| A2B𝐴2𝐵 | The square of the bullet's axial moment inertia divided by its transverse moment of inertia |
Bullet Gyroscopic Stability Calculator
Calculate the Gyroscopic stability of a bullet with the Miller approximation.
bisonballistics.com
I remember watching a long range Rimfire video, could have been at 1000. The bullets were still oriented tip forward, but the trajectory was such that they impacted pointed pointed significantly downward.
ammo gets less accurate every hundred yards out to about 400 where is much less predictable. some rifles with good barrels and ammo will still group at 400, some wont. nothing will group tightly at 500...
IMHO the stabilty limit or window of unpredictably flight is somewhere 350-450, ie its a pretty narrow band.
Thanks, I was just wondering if there was any standard of accuracy at 500 or beyond.
I shoot quite a bit at 600, at 4700 ASL, and if there is unpredictability, it is atmospheric conditions, not so much rifles or ammo, both 16tw and 13tw barrels.
I've had a couple decent days at 700 also, and we are talking calm days, and for 1day around Christmas last yr, we were hitting 800 with relatively< keep in context, accuracy, both 16 tw Vudoo and 13tw Rim X, Lapua and RWS ammo.
We TRIED 850 & 900 the next day, with a March Genesis mounted and failed miserably, why I am in this thread.
800 yards, 4 mags Rim X, 20rds on the 12" plate, 20rds at the paint can, we weren't missing by much. The Vudoo connected on a 24" plate earlier that day, but no resemblance of accuracy, also no indication of tumbling.
The dogshit b.c. of .22LR leaves me to not to even worry about losing stability.
At 300yds, the groups are usually bigger than I find practically useful if we have much more than mildly windy days. And energy on target is probably lethal enough. But the majority of the bullets are round nose....so they suck ass for terminal performance even close in.
Basketball group sizes don't excite me. Being off by 1mph wind means I burn off both sides of the plate don't excite me.
I know that shit is stable a bit further out but who cares. Your more or less flinging and hoping at a certain point. I can grab a centerfire and go back to being sanely effective again.
You wanna do 2" hangers at 200yds? Sure sign me up.
You wanna do the 300yd beer can challenge or gophers. I'm in. Harder but fun.
But worrying about the stability? GTFOH
You don't need weaponized math. We've got ballistic solvers and written "try dope" everywhere for reference.
At 300yds, the groups are usually bigger than I find practically useful if we have much more than mildly windy days. And energy on target is probably lethal enough. But the majority of the bullets are round nose....so they suck ass for terminal performance even close in.
Basketball group sizes don't excite me. Being off by 1mph wind means I burn off both sides of the plate don't excite me.
I know that shit is stable a bit further out but who cares. Your more or less flinging and hoping at a certain point. I can grab a centerfire and go back to being sanely effective again.
You wanna do 2" hangers at 200yds? Sure sign me up.
You wanna do the 300yd beer can challenge or gophers. I'm in. Harder but fun.
But worrying about the stability? GTFOH
You don't need weaponized math. We've got ballistic solvers and written "try dope" everywhere for reference.
One of the most popular shoots in the country is NF ELR match, fills up immediately, shooters travel far and spend a ton of money on equipment, lodging, etc..., and I'd bet the overall hit pct is less than 50% overall.
ELR shooters spend even more to basically miss past a certain point.
Missing is exciting when doing what most won't try, lol. I may be trying to convince myself of this as much as you.
How many of those are people who don't shoot regularly and just want something to do. Lol
Are you telling me that we clearly are not in a recession?
Oh I'm not against people spending their money out pushing boundaries. I against wasting my money after trying and seeing what progress I am personally seeing for the funds I am willing spend.
But if guys wanna fund Lapua executives' retirement paying $150 a brick or more for not much in return....more power to them.
2020, approx 85% NF ELR competiors were under 2moa in their Scored groups at 1,000 yards (in a electronic target stage), yet ~ 50% of the target arrays were < 2 MOA in one dimension...which is why this was a hard match.
I was just making a slight comparison of what it is worth to miss to some people. If 300 was a cap for me and 22LR, I'd sell mine, and some days, you have to set steel closer.
I learn more from misses than hits, hit is a hit, misses make you pay attn.
I think this is where a lot of shooters have trouble....they can't learn from there misses.
Nearly all small arm projectiles experience dynamic instabilities deep in subsonic region (0.5 Mach and down). Sooner or later, a slow mode coning amplitude starts to grow during the flight. In most of the cases this is going to result in a limit-cycle yawing motion. Sometimes pitching & yawing motion can be quite remarkable with total angles of attack like 10-15° and projectiles can fly for a really long time like this. But if the slow mode coning amplitude grows further without bounds, the projectile will tumble. IIRC, as concerns 22LR, CCI quiets, fired from 1 in 16" TR barrels, are "key-holling" at 300 yards. Of course 300 yards for CCI quiets is of zero practical importance (except maybe not for crazy ballistic junkies who like to do crazy tests)
