twist rate and bullet length
- Thread starter shootsteady
- Start date
Good article German!
It does seem to be saying something which runs counter to conventional wisdom though, that bullets become less stable with distance. Since bullets lose very little rotational velocity in the half second they're in the air....... those loads must have been VERY marginal indeed!
LOL
al
It does seem to be saying something which runs counter to conventional wisdom though, that bullets become less stable with distance. Since bullets lose very little rotational velocity in the half second they're in the air....... those loads must have been VERY marginal indeed!
LOL
al
O
Old Gunner
Guest
If you like to check the Figure Of Merit and Mean Radius figures of military ammuntion acceptance testing of WW2 and earlier I think you may find that reduction in divergence was recognized early on.
Recognized? Or simply misinterpreted data? Many assertions and theories have been disproved over time. Now that we can directly measure stuff we find many theories being thrown into question or more often simply disproved.
Or, like in the case of Marine Corp ballistics theory, concepts like bullets "rolling on the air" are just passed down because the average shooter doesn't have to know "why" just "what."
al
O
Old Gunner
Guest
Bernoulle's principle has been known since 1738, if you mean the unscientific terms such as bullet drill and such then its just a matter of not fully unuderstanding the mechanics that produce the result.
The Magnus effect is well known.
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Thank you for making my point!
This is exactly the sort of stuff I was referring to. Bernoulli's Principle and the Magnus Effect have been used in descriptions of the mechanics of Gyroscopic or "spin" Drift.Read and understand Vaughn and McCoy to see the real causes, gravity and air pressure.
A bullet is not a curve ball. Skin and boundary layer effects are negligible to non existent for a supersonic projectile.
al
Stephen Perry
New member
OK my good shootin long range buddies the new guy has his yardages messed up we have all done that especially when new. Noboby on the planet shoots 3/4" groups at 300 yd with a sporter gun barrel assumming some kind of factory Savage or Remington. Review your yardages new guy. You are talking to the wrong crowd here. Alinwa, Larry, and German do this shooting stuff for a living, I do it as a BR guy and a varmint guy part time. Back in the 1970's with full blown benchrest rigs the World Records were in the .5 range now they are better but that is with 30+ years of shooting. Hi Power guys that shoot a steady diet of 300 shoot maybe 1 1/2 MOA at 300 correct me here German.
As far as 55 grn bullets in a 22-250 those are the bullet weights that a 22-250 has been shooting since 1915 when the then wildcat 22-250 was developed. Read some Sierra manuals, Hornaday, Speer, Nosler and any bullet maker that makes 22 bullet info.
Not aimed at you directly new guy, mainly more at Savage guys that claim phenominal accuracy that we all know is BS over here, but I would revise your Thread with correct info. I'm nicer that alinwa , al is a good guy, but not on Round 2.
Stephen Perry
Angeles BR
As far as 55 grn bullets in a 22-250 those are the bullet weights that a 22-250 has been shooting since 1915 when the then wildcat 22-250 was developed. Read some Sierra manuals, Hornaday, Speer, Nosler and any bullet maker that makes 22 bullet info.
Not aimed at you directly new guy, mainly more at Savage guys that claim phenominal accuracy that we all know is BS over here, but I would revise your Thread with correct info. I'm nicer that alinwa , al is a good guy, but not on Round 2.
Stephen Perry
Angeles BR
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Agreed, that is seriously Ragged Edge....
My one little anecdotal "test" in this regard concerns my Sako 6PPC which has a very loose 14 twist..... closer to 15. As the temperature falls you can watch it go from bugholing 70NBT's to laying them sideways through a 40degree temp range at 30% humidity and 1000' MSL.
And before it lays them sideways it gets some really squirrely fliers..... in my mind the bullets are flying like those shrieking Saturn Missiles on the 4th of July
I've fired a lot of bullets through various twists just to see if they're stable but this little Sako is the only one where I've watched it transition as conditions changed.
fun stuff
al
shootsteady
Member
thanks for all your input guys..... sometimes I have to aggrivate people in order to get some real concrete answers, again thanks.
Stephen Perry
New member
SS
Your form of aggravations is what causes harsh words to fly. Consider that guy with no name and a bad handle.
I will not Post on your stuff anymore. That's the way it is. No such thing as 300 yd groupings with a factory rifle like the accuracy you claim.
Stephen Perry
Angeles BR
Your form of aggravations is what causes harsh words to fly. Consider that guy with no name and a bad handle.
I will not Post on your stuff anymore. That's the way it is. No such thing as 300 yd groupings with a factory rifle like the accuracy you claim.
Stephen Perry
Angeles BR
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Well back in '94 I hadn't really gotten into ballistics, was just exploring the fringes of accuracy. I had an idea that somebody could figure the stuff out, and had found the Shilen twist rate chart on the internet but that's about the extent of my interest. I was busily trying to find the ultimate all-round competitive setup and desperately trying to show that "intrinsic accuracy" was a myth. LOTS of money and shootin' and tryin' and not so much settin' and thinkin'!
It was the Brute Force Approach to accuracy.
Interestingly enough, I worked up the load in the hot springtime, 80 degrees or so and loading at the bench I found the 70gr Ballistic Tips to be accurate and reasonably priced.... I loaded a bunch up for a squirrel hunt up at 5500' in the hot high desert of Eastern OR and did well with them.
It kinda' became "the go-to load" in my mind...... I set the leftovers aside and moved on to other rifles. Couple winters later I dragged 'er out for a friend and. . . . HUHHH????
Long story short I found out what your numbers are saying
The hard way. I pulled the bullets.
LOL
al
O
Old Gunner
Guest
Never implied that the bullet's path curved, or that its path somehow converged.
Don't know what you are visualizing but it doesn't match what I said about overcoming initial yaw, or the effect of that temporary yaw on the short range group.
I won't bother going into it further.
shootsteady
Member
Seems to me gunner, that theses guys really don't know what they're talking about, anyway....
LOL!!!
Nope you won't, because you can't......
For those who're wondering, here's Bernoulli >> http://en.wikipedia.org/wiki/Bernoulli's_principle << Bernoulli explains airplane wings and carburetors and scavenging flows .............. Bernoulli first explored the velocity/air pressure conundrum and explained why IN AIR a wing or propeller can produce lift without angle of attack. (It doesn't work in water) Bernoulli and his kissin' cousin Venturi explain all sorts of things, but not much about supersonic projectile motion!
And Magnus: Let's not forget Magnus, sounds meaningful and impressive..... MAG'nuss.... WHEEeeeee, RIGHTeous Dude!!! ..... >> http://en.wikipedia.org/wiki/Bernoulli's_principle << Magnus rearranges and applies Bernoulli's Effect as generated by surface friction drag and applies it to curve balls... and in this (misguided) wiki it agrees with Old in misapplying the effect to bullets. The wiki's wrong, Old is wrong and steady is looking on and cheering for his favorite, doesn't have a clue
.... this BTW is the strength and curse of Wikipedia. I should go correct it but won't. I'm so burnt out on trying to argue with silly people...... and there are no applicable cites on line. N-R has it sewed up until someone transcribes McCoy or Vaughn.This is a beautiful solution all-round really, Old and steady can be "right" based on this wiki. It's a real cite!
(BTW guys.... you wanna' REALLY gain credence with your educationally challenged rooting section you can use my lead and point and clik your way to Nunnsteil Rupprecht to see more about bullets slipping and sliding and rolling on the wind..... complete with impressive looking equations in cool colors and fancy script
This site is so believable that it draws backyard ballisticians like flies)And Coriolus, let's not forget Coriolus, somebody's gonna' drag HIS sorry ass in soon if we talk about spin drift....
But.... bullets ain't curve balls.
And two paths diverging in the wood CANNOT get closer together, relatively, without curvature occurring. That's angular divergence ... lay two pool cues or cane poles on the table to visualize it.....
bummerdealdude
Perty soon someone will link in the MOAWDT and we'll really heat this thang up!!!
lol
al
And BTW Old Gunner..... I DO understand your contention. If I were to guess (since you won't get into it
) I'd guess you're referring to "epicyclic swerve" as the explanation for groups "diverging less with distance" (yet not curving...) For those who're wondering where the information can be found please purchase 'Modern Exterior Ballistics, The Launch And Flight Dynamics Of Symmetric Projectiles' by Robt L. McCoy. Chapter 9, Six-Degrees-Of-Freedom and Modified Point-Mass Trajectories,' explains it well. There's even a stylized illustration (picture, steady) in chapter 11.4 'Discussion of the linearized swerving motion' which has led many to believe that it's at least theoretically possible for groups to converge (Sorry Old, "diverge less" )And ALSO BTW....... while you're at it read section 2.12 'Neglected forces and moments' to see the effect of Magnus in real life.... I'll quote just a little of it.
"Neilsen and Synge (ref. 2) first showed that the Magnus cross force and cross moment must be retained in order to preserve logical consistency in our aerodynamic force-moment system for spinning symmetric projectiles. However, free-flight spark tests have never been able to measure this force or moment; they produce such insignificant effects on the trajectory that even a high precision spark range facility cannot detect them. The Magnus cross force and cross moment will be defined but not illustrated, since they are included only to preserve logical consistency."(bolding mine)
((((What this means is, it's like a single grain of sand on the beach. Yup, it's THERE, but adding or removing a grain doesn't change the character of the beach))))
hth
al
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1000mstudent
Guest
excellent thread, educational.
Would someone explain to me how much temp will effect the bullet's stability. I'm shooting in the foothills outside of Calgary. In the winter we can have wide swings in temps. In a single day the temp can change due to chinook winds, from -15f up to 35f in a matter of a few of hrs. No bs. I do shoot in the cold and am told I'm insane:, but it's not too bad if you dress for it.
Would someone explain to me how much temp will effect the bullet's stability. I'm shooting in the foothills outside of Calgary. In the winter we can have wide swings in temps. In a single day the temp can change due to chinook winds, from -15f up to 35f in a matter of a few of hrs. No bs. I do shoot in the cold and am told I'm insane:,
but it's not too bad if you dress for it.
L
Larry Elliott
Guest
excellent thread, educational.
Would someone explain to me how much temp will effect the bullet's stability. I'm shooting in the foothills outside of Calgary. In the winter we can have wide swings in temps. In a single day the temp can change due to chinook winds, from -15f up to 35f in a matter of a few of hrs. No bs. I do shoot in the cold and am told I'm insane:,
As far as I know the bullet doesn't care what the temperature is except for air density, but the powder does. If things are on the ragged edge of stability at 35° F, the powder is likely not going to produce the same pressures and velocities at -15° F. They'll likely be enough lower that the bullets that were ragged edge at 35° are now unstable. The denser air at lower temps might well not help either.
The weather in Montana can do the same thing, but as I've gotten older I haven't gotten any smarter - maybe some dumber - but my delicate sensibilities are more easily offended by sub zero temps. A little breeze doesn't help at all either. I envy your toughness.
Stephen Perry
New member
I just added this Thread to my favorites. Keep taking Larry, Alinwa, and German, fruitfull.
Stephen Perry
Angeles BR
Stephen Perry
Angeles BR
1
1000mstudent
Guest
Thanks for the answer, I set up a tent to keep the wind off me and have a thick foam PL 300ed to the 1/2" plywood under me. It works well. Not so tough, just prefer to use brains over brawn.
O
Old Gunner
Guest
I'm sure they know what they are talking about, it seems they are over thinking the situation and don't take into account that what happens in one instance may have little to do with a very similar instance that depended on irregularities in mass production military and sporting ammo with very different qualities than what they've become used to.
I had typed out a fairly detailed, and probably easily understood explanation, but decided to delete it, as I don't think it would get through.
Just remember that I wrote "in some cases", what can happen in some cases is often not repeatable as an experiment when there are so many factors that can combine.
One need only look to experiments in the penetration of AP cores at varying ranges to see that initial yaw is a very important factor in bullet performance.