Bullet stability vs flight time

[urcayuse]

Playing with some loads today ,just barely MOA @ 100yds. Yet they are sub 1/4 MOA at 570. Do some bullets require some flight time before they get stable? Does'nt seem to make sense but i've found this to be the result twice. Any more experienced guys out there get similar results?

[Comstar]

Originally Posted by urcayuse

,just barely MOA @ 100yds. Yet they are sub 1/4 MOA at 570.

1/4 inch at 570! Nice shooting! Lol I wish...

[elkhunter11]

1/4 inch at 570! Nice shooting! Lol I wish...

1/4moa at 570 yards, is a far cry from 1/4" at 570 yards.

[260 Rem]

If a bullet groups 1MOA AT 100yds it will produce a group of just over 5" at 500yds unless the wind blows 'em all back towards the center. Typically, only very gifted shooters with good eqpt can maintain the same accuracy at distance as they get at 100yds. One thing you can count on, is that once a bullet sets out on its path..it does not "steer" back on course! It does not "go to sleep" or get more stable. If you are getting consistent 1/4MOA groups over 500yds, you are IMO a gifted shooter.

[catnthehat]

The theory (and arguments!)of bullets going to sleep or not has been argued back and forth since arrows were invented.

I once had a Rub-ger No.1 V in .223 that drve me nutzy cuckoo.
it's 100 yard groups were no tighter than the 200 yard groups, which were respectable but not real zingers.
I talked to a couple of well known shooters about itwhich spaqarkewd the age old battle!
I then asked the old man, (who himself was a very respected ballisician within the industry) who told me to shoot ten more groups and get back to him.
Hmm, it's amazing how the avaerage of three groups can be so much different than ten groups!!
Trigger time with the rifle was the variable in that case.
YMMV

Cat

[twofifty]

quote:
"Hmm, it's amazing how the avaerage of three groups can be so much different than ten groups!!"

That there's a keeper.

[DaleJ]

Originally Posted by 260 Rem

If a bullet groups 1MOA AT 100yds it will produce a group of just over 5" at 500yds unless the wind blows 'em all back towards the center. Typically, only very gifted shooters with good eqpt can maintain the same accuracy at distance as they get at 100yds. One thing you can count on, is that once a bullet sets out on its path..it does not "steer" back on course! It does not "go to sleep" or get more stable. If you are getting consistent 1/4MOA groups over 500yds, you are IMO a gifted shooter.

One MOA at 100 is 1" or close to it. Quarter MOA at 500 yds 1.20". The group is still larger at 500 yds. Further down OP mentions 5-shot group at 100 versus a 3-shot at 500. This happens, been there, done that. Never had groups shrink as the distance increased but shot lots of disappointing 100 yd groups that did not triple in group size at 300 yds. I do a bit of long range shooting and usually don't bother shooting boat tail bullets at 100 yds anymore. 1/4 MOA at 500 yds ain't that tough if conditions are good.

[260 Rem]

1/4 MOA not tough at 500yds ... WOW!!! Just reading an article by Sam Hall about one of his "heavy 6MM Dashers. (Sam is described in the 6MMBR introduction to his article as being "one of the greatest middle-distance class benchrest shooters on the planet"). When Hall was shooting his 6.5 X 284 he only shot one group under 2" at 600 yds in a whole year. When he changed to the 6 Dasher, he was able to agg under 2". He came second in Piedmont with a 1.76" group and the World Record was set with a 1.46" agg group score. Hall uses a couple of Dashers ...one weighs 28lbs and the other 60lbs.
Dale, it appears your 1/4 MOA groups at 500yds are in World Record territory..even when competeing against those big heavy custom jobs. Great shooting --- Are you going to be competing in the near future? What rifle and bullets are you using? I'm looking at building a 6 Dasher, but my mind could be changed by whatever you are shooting as it seems superbly accurate.

[gitrdun]

Originally Posted by Comstar

1/4 inch at 570! Nice shooting! Lol I wish...

1/4 MOA = 1.425" @ 570 yards BTW.

Flat base bullets stabilize much faster than a boat tail at ranges up to approx. 200 yards in the. 223 rem. Boat tails take longer to stabilize but really come into stabilization at longer range where the FB bullets start to wiggle.

[urcayuse]

The hundred yard groups were 5 shot and the 570 was 3 shots, so maybe not a real fair comparison.I checked out Bergers web site and they actually mentioned that the vld's might not group all that well @100yds. I'll try some more tomorrow.

[260 Rem]

Originally Posted by urcayuse

The hundred yard groups were 5 shot and the 570 was 3 shots, so maybe not a real fair comparison.I checked out Bergers web site and they actually mentioned that the vld's might not group all that well @100yds. I'll try some more tomorrow.

I think Berger prefaces their comment with "some shooters have reported that VLD's do not group as well at 100yds" ... which I assume refers to some shooters experiences when compared with flat based bullets shot in short range competion. I don't think they meant the same VLD achieved better MOA group results as they got further away? I think most short range competion shooters use flat base bullets?
Further, it is my understanding that flaws on the muzzle crown will cause gasses to mess with accuracy...but, the muzzle blast from an evenly cut crown with no scratches, does not upset bullets. Could be that part of the comparison between the accuracy of flat vs. boat-tail designs have to do with the fact that it is easier to create a perfectly flat base than it is to do the same on the boat-tail?

[PoppaW]

I have a gun that shoots 4moa on paper but never misses the mark on big game. I have calculated the corkscrew effect and it is not enough to explain what I am seeing. I now use the 'cork' effect or 'shot' glass formulas. After a few calculations I don't want to go shooting anymore and it doesn't matter.

[Tactical Lever]

Originally Posted by 260 Rem

I think Berger prefaces their comment with "some shooters have reported that VLD's do not group as well at 100yds" ... which I assume refers to some shooters experiences when compared with flat based bullets shot in short range competion. I don't think they meant the same VLD achieved better MOA group results as they got further away? I think most short range competion shooters use flat base bullets?
Further, it is my understanding that flaws on the muzzle crown will cause gasses to mess with accuracy...but, the muzzle blast from an evenly cut crown with no scratches, does not upset bullets. Could be that part of the comparison between the accuracy of flat vs. boat-tail designs have to do with the fact that it is easier to create a perfectly flat base than it is to do the same on the boat-tail?

Muzzle damage will of course affect accuracy, as will powder selection, barrel harmonics, load density, bullet to rifling contact length, twist speed, sectional density (bullet length to caliber ratio affecting rifling contact area), as well as factors I'm sure that I'm leaving out.

Damage or accuracy problems notwithstanding, all "high" velocity bullets leaving a "normal" length barrel will be passed by a jet of still expanding gases travelling at approximately mach 5. Whereupon shortly after leaving the muzzle they will be rapidly slowed (and cooled) to below bullet speed and then below speed of sound. As the gas cloud slows it creates turbulence coming from a rapid pressure change that the bullet then passes through.

This rapid pressure change and turbulence associated with it, creates a shock wave, similar to when a jet passes through sonic transitional speed, and slightly and temporarily destabilizes the bullet similar to the way a gyroscope would be if it was tapped.

Supposedly the flat base is less affected by this, which is why it is favoured for 100 yd. matches; an advantage that is lost at long range as the boat tail drifts slightly less, drops less and stays super sonic a little farther.

[DaleJ]

Originally Posted by urcayuse

Playing with some loads today ,just barely MOA @ 100yds. Yet they are sub 1/4 MOA at 570. Do some bullets require some flight time before they get stable? Does'nt seem to make sense but i've found this to be the result twice. Any more experienced guys out there get similar results?

Makes no sense to me either, but its happened a few times. I thought it was a parallax problem until it happened again with peep sights. Bryan Litz in his Applied Ballistics book calls this the "epicyclic swerve" or corkscrew trajectory. Google epicyclic swerve and several you-tube videos will pop up. There is one that shows time of flight as well as distance traveled.

[Cal]

I've got a .223 that consistantly shoots as tight of groups at 200 yards as it does at 100, heard of such things before but I sure dont understand it.

[260 Rem]

Can't recall the exact effect of the "corkscrew" calculation, but I think it is in the neighborhood of .05" at 100YDS.... and kind of strange how that corkscrewing and sleepy bullets only surface with some rifles in spite of the fact that they are all spinning. First, shooting three shot groups can skew results dramatically. Second, a few groups do not an average make...I wish they did 'cause with some cherry picking most shooters could post some impressive stats.

[hardy]

I have an article by precision shooting that was talking about groups getting smaller at a farther distance because of the scope having a proper parallax at a farther range. Therefore the scope and rifle could actually be aimed more precisely, which in turn produces better groups. Just something else to think about.

[urcayuse]

Originally Posted by DaleJ

Makes no sense to me either, but its happened a few times. I thought it was a parallax problem until it happened again with peep sights. Bryan Litz in his Applied Ballistics book calls this the "epicyclic swerve" or corkscrew trajectory. Google epicyclic swerve and several you-tube videos will pop up. There is one that shows time of flight as well as distance traveled.

Just watched the video , thats pretty cool stuff thanks

[Tactical Lever]

I read a pretty good sounding theory on it once. It being that as the bullet exits the barrel it is subjected to muzzle blast of hot gases going past it at approximately 6000 fps which temporarily destabilizes the bullet. The bullet as it is spinning, recovers and loses the wobble that may have been imparted to it. Much like a gyro-scope that has been tapped and allowed to recover.

Can't say that I have experienced it myself. Probably wouldn't notice if I did!

[Hotwheels81]

And here I just blamed thick crosshairs...

[Speckle55]

Originally Posted by urcayuse

Playing with some loads today ,just barely MOA @ 100yds. Yet they are sub 1/4 MOA at 570. Do some bullets require some flight time before they get stable? Does'nt seem to make sense but i've found this to be the result twice. Any more experienced guys out there get similar results?

here is Brad Sauve talking on his best load in F-Class shooting.. and yes to some bullets being more stable at longer ranges when shot with the right bullet shape and fps all other things being equal..
the US F-class team is shooting 180 grain PP in 1000yds matchs this year

F-Class is Palma for us old guys or some of us have used our
scopes and rifles for this Long Range Shooting for over 30 yrs

we have a 530 yds at our range www.Hintonfishandgame.ca


Food for Thought

David

But I finally found my "sweetheart" load on February 14, 2000 (Valentines Day), almost seven months after getting the rifle. This is the load I still shoot today and I shot all weekend at the F-Class Nationals. The break-through came when I discovered that slower velocities produced outstanding accuracy. I found that Varget pushing a 175 SMK at about 2610 fps delivered quarter-MOA groups out to 300 yards and half-minute or better groups beyond that distance. Since developing that load, I've used Lapua cases and Russian primers, but the core elements, 43.0 grains Varget with 175 MKs seated 0.018" off the lands, has not changed.


http://www.youtube.com/watch?v=VB4NGNaKnhE

[catnthehat]

Actually , Fclas and alma are two colmpetly different dicsiplines, one is used with a resat or bi-pod and optics and the other is used with sling 'n' irons.

There are two distinct clases of Fclass, and but no different equipment classes for palma.

Cat

[Speckle55]

Originally Posted by catnthehat

Actually , Fclas and alma are two colmpetly different dicsiplines, one is used with a resat or bi-pod and optics and the other is used with sling 'n' irons.

There are two distinct clases of Fclass, and but no different equipment classes for palma.

Cat

for us Old guys;;;;; yes on the different equipment classes

[catnthehat]

Originally Posted by Speckle55

for us Old guys;;;;; yes on the different equipment classes

Fclass has also turned into very much an equipment race, what with a zillion different cartridges and stocks out there, whgereas palma is still very strict on stuff like trigger pull weight, gun weight, cartridge used, etc.
The fact remains owever, tha the best shooters are still winning both dicsiplines.....
Cat

[Speckle55]

Originally Posted by catnthehat

Fclass has also turned into very much an equipment race, what with a zillion different cartridges and stocks out there, whgereas palma is still very strict on stuff like trigger pull weight, gun weight, cartridge used, etc.
The fact remains owever, tha the best shooters are still winning both dicsiplines.....
Cat

Yeah the older Palma shooters are loving F-class .. as you say they were shooter's in Palma and now with their eye not as good the switch to F-class

i have iron sight but have used scoped rifle since the seventies.. but i did vent that Black Wolf the other day with the 94 at 20 yards.. lmao

David
http://www.chuckhawks.com/f-class_shooting.htm