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Old December 29, 2012, 08:09 PM   #1
overthere
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Accuracy at different distances

For those of you who have reloaded for a long time and shoot at different distances, will a load that works well at 100 yards typically also work well at 300 or 600 yards?

I have been trying out different powder and bullet combinations for my .223 bolt action, shooting at 100 yards. I have found a few combinations that yield very good accuracy (1 MOA or less) and I was planning on taking these to 300 yards to try them there.

Is it valid to identify an 'accurate load' at 100 yards and then take that to 300 yards and expect it to perform well at that distance too? Or is it that something that works well at 100 could stink in terms of performance at 300 yards? What about when going to 600 yards?

How much difference does bullet weight and velocities make when going to longer distances? For example my rifle likes 68 gr Hornady Match bullets with either 23 grain or 25 grain Varget (but not the charges between those two). Would the 25 grain load be more accurate at 300 due to the (presumably) higher velocity?

The rifle is a Savage 11 with a 1 in 9 twist.
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Old December 29, 2012, 08:21 PM   #2
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Some will do great at 100 yards, and then not so great at 300+. It is one of those things that you will have to experiment with. I can say I have never heard of loads that shot awful at 100 yards, and did great at 300+.

I would say if it works very well at 100 move it out, and test it.
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Old December 29, 2012, 08:22 PM   #3
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just my opinion here but what shoots good at 100 may or may not shoot well at 800 but what does not shoot well at 100 will definitely not shoot well at 800. I do my load workups at 100 where wind etc will have minimum impact, then move the best loads to 200, then 600 then 800. I have never had a load yet that shot so so at 100 then suddenly tightened up at 800 but then I have only been playing at long range for a couple of years now so it could happen. I suppose. Just speaking about myself here but the indian screws up more than the arrow does at long range
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Old December 29, 2012, 08:57 PM   #4
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There are two different schools of thought on this.

There is the empirical, measure groups at two locations to see if there is a change group, and they have found using screens that MOA doesn't change with distance.

The other group is the "yaw stability" group and they show that bullets do increase in stability during time of flight.

Personally I've had loads that didn't group very well at 100 (right at 1 MOA) go into a 1.5" group at 200 (0.75 MOA) rather consistently. This led me to believe that after the initial yaw instability of my bullets was overcome by aerodynamic forces, that it would be a 0.75 MOA group at pretty much all distances up to the transonic zone (when weird things start happening to some bullets).

That is just my experience, using a 308 Win and 168gr HPBTs. The article I read about using screens to measure MOA at multiple distances for the same shot group was using a benchrest rig if I recall correctly. Benchrest bullets are known for very good imbalance and stability even at short range.

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Old December 30, 2012, 12:35 AM   #5
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Jimro, would you happen to have any links to either the screens test or anything related to the 'yaw stability' topic? I would like to know more about both of them.

Thanks
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Old December 30, 2012, 12:56 AM   #6
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Here is a good resource for how bullets fly: http://www.nennstiel-ruprecht.de/bullfly/

I'm still trying to remember where I read the article on MOA testing at different ranges. I think that might have been two or three computers ago :P

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Old December 30, 2012, 01:47 AM   #7
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Thanks Jimro.

Fascinating paper, I do not claim to understand all of it but pages like the following does a great job (I think) explaining why the point of impact can be so different with different bullets even if the powder charge is the same. No such thing as a (true) straight line from point A to point B for bullets.

http://www.nennstiel-ruprecht.de/bullfly/fig13.htm

Reading that paper and looking at ballistics charts for different calibers it is close to mind boggling that long range shooting is possible and predictable
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Old December 30, 2012, 05:53 AM   #8
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Most of my "hunting " loads I work up at 200yds instead of 100 for that particular reason. If they shoot 1" at 200 then I am good to go at anything closer, and usually quite a bit further.

That said I also shoot heavier for caliber bullets in most of my loads as well. THese may or may not be in the optimum range for stability, in that particular rifle.

WHen I was working up loads for 1K, I found that while getting on paper at 100 was useful, any loads I dialed in there were pretty much useless past 400. Not that they wouldn't hit in a 6" circle, but they weren't nearly as acurate as the ones I worked up at 2-300yds.

WHen you get into shooting the longer ranges you usually looking at using a longer bullet for caliber as well as a bit faster twist to stabilize it. You are for the most part also right on the ragged edge of stability for those particular bullet at the initial velocities from the muzzle, but after 2-300yds the velocity drops and the rotational stability takes over and the bullets "go to sleep" as it's called. Once there you can easily see groups tighten up further out than up close.

My 1K rifle shoots around 2" at 100 on average, but will the same load will shoot around 1-2" at 500 if I am on my game and will group around 8-9" at 1K depending on again me doing my part. The load that I worked up initially at 100 won't even stay on target at 600 as it continually spreads out as the distance increases, but it looks good at 100.

With my 25-06 1-10 and 26-06 AI with the 1-9 twist, I shoot 120 and 130 grain bullets. THe 120's will stabilize wonderfully in my standard version but the 130's are lucky to get within 3" at 100. With the AI version, I am getting 1-1.5 at 100 with either of them but at 300 they are both down to 1" or less most times. These are being pushed to 3350 form the 28" barrel where as the 24" on my standard rig will only get mid to high 2900fps from the 1-10. They start out faster in the 28", but also spinning faster as well so there is a bit of over stibility to overcome before they settle down and fly true.

I know this was a bit much but it is the examples I have to relate, based upon what I have seen first hand.
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Old December 30, 2012, 06:02 AM   #9
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Dr. F. Mann proved with slow, heavy lead bullets that corkscrew bullet path happens in the early 1900's. Sierra Bullets also noticed it happening. Note Sierra's bullets were spinning and traveling much faster than the lead ones Dr. Mann used. Sierra also felt that the corkscrew path pretty much settled out in the first 100 yards; they've "gone to sleep" at that range. But the size of it was pretty small else they would not have shot so many groups in the ones at 100 yards in their test range. If you look at the groups fired in 100 to 300 yard benchrest, they're bigger in angle as the range gets longer.

I don't trust data on group angular subtention getting smaller as range increases when group A is fired at a different range than group B. And compensation from barrel whip certainly causes lower velocity bullets to strike the same point of aim at some long distance as higher velocity ones. The Brits proved this over a hundred years ago as documented in the following article "Vibrations of Rifle Barrels (January 1, 1901)"

http://archive.org/details/philtrans05900167

Click on the "PDF" link in the upper left-hand "View The Book" cell to read this facinating article. No wonder those .303 SMLE"s shot so darned accurate past 500 yards all the way to 1000 with arsenal ammo compared to Mauser 98 style rifles. But this just corrected vertical shot stringing. It's also been observed testing M14NM's in accuracy cradles and their 600 yard groups were a bit smaller angle wise than those at 300 yards with the same ammo and rifle. Gas escaping from the port mid point in the barrel bent the barrel up at that point making the muzzle axis point lower if gas pressure was higher making faster bullets leave at a lower angle; slower ones with lower pressure leave at a higher angle.

As virtually all bullets are unbalanced, they'll all wobble, nutate, cone or in someother way fly through the air like a poorly passed football in the Super Bowl. A few fly perfect. All the rest wiggle as they fly. The more they wiggle, the more drag they have. With more drag, they slow down faster. So the wiggly ones drop less at a given range; they strike lower than faster ones. Their BC ain't all exactly the same. Sierra Bullets conducting time of flight tests has observed this. Their best match bullets have about a 1% spread in BC because of it. All bullet makers' bullets have the same problem; some to a greater degree than others. After a friend spun a bunch of bullets in a balance measuring tool and shot only those with perfect balance, they shot a1 inch or so 10-shot groups at 600 yards. Some of those bullets were so bad they flew out of the test collet spinning 30,000 rpm.

I don't know of anyone in the last several decades that's shot a given bullet through screens every few yards all the way to at least 500 yards to show how a single bullet prints relative to the line of sight at each range. If it's been done and there's a link to it, please post it.

About both vertical and horizontal group size, can anyone who can explain how a bullet at the right hand part of an aerial group at short range knows how to change direction to the left back towards the center of an aerial group at a longer range, each and every time it's in that place? Please elaborate.
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Old December 30, 2012, 10:51 AM   #10
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Quote:
I don't know of anyone in the last several decades that's shot a given bullet through screens every few yards all the way to at least 500 yards to show how a single bullet prints relative to the line of sight at each range. If it's been done and there's a link to it, please post it.
Sure would be interesting, and the technology sure is there.
With the growing popularity of long-range shooting, one would wonder if there hasn't been "secret testing already done by the likes of Berger, Sierra, or others that are consistently trying to raise the bar.


To the OP, google "ladder test", which is a method of load development preferred by some long range shooters (over, say, OCW) IF they have the distance available to shoot.

The longer the range with load development, the more apparent the subtle differences become. In short, what might be barely noticeable in a 100 yard grouping becomes much more visible at 300-500. You're looking for vertical spread, discounting horizontal drift due to wind.
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Old December 30, 2012, 12:06 PM   #11
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Wow, lots of great information.

The 1901 paper on barrel jump is awesome. Besides being fascinated by the content and the explanation of the effects of barrel harmonics I kept thinking of how they did all the graphing before there were computers I wonder how long it took the author to create Diagram 11 on page 14 of the PDF by hand.

Thanks for the tip on ladder testing, found this link which has a great step-by-step description http://www.6mmbr.com/laddertest.html
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Old December 30, 2012, 12:30 PM   #12
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Quote:
About both vertical and horizontal group size, can anyone who can explain how a bullet at the right hand part of an aerial group at short range knows how to change direction to the left back towards the center of an aerial group at a longer range, each and every time it's in that place? Please elaborate.
Newtons first law would make groups tightening up impossible, great post btw
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Old December 30, 2012, 12:48 PM   #13
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I've had more "404" errors trying to find references to group testing at different ranges than any time since I tried to find the "concept of design" for reloading article...

On page 2 or three of this thread "alinwa" explains his testing at different ranges.

http://benchrest.com/showthread.php?...-with-Distance

Bryan Litz used acoustic screens to test bullet flight every 200 yards, but his old personal site is offline now. I'm not going to pester him for the data.

The common theme with these test setups with acoustic screens is that no one tracks the initial instability of the bullets in the first 50 to 80 yards.

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Old December 30, 2012, 01:05 PM   #14
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I recall a post on one of the benchrest boards about downrange accuracy.
The shooter had one of the Oehler accoustic targets set at 100 yards and a regular target at 334 yards. He said that in no case was a group at 334 tighter in MOA than at 100.

The corkscrew diagrams in the nennstiel papers are deceptive. They show the yaw of the axis of the bullet, not some sort of orbit around the line of fire. The NRA once figured that the air spiral of a .30 bullet was a maximum of .1". This might get you an oval hole in a near target before it damps out, but there is no restoring force to bring a bullet back towards the center of a group shot with other bullets.
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Old December 30, 2012, 02:41 PM   #15
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In Dr. Mann's book, Part II, starting on page 268:

http://castpics.net/subsite2/Classic...r_to_targe.pdf

There's excellent graphs and pictures showing how unbalanced bullets spiral around the trajectory axis. Also shows his cards aligned on his test range so the bullet paths could be graphed. Read the whole book; interesting stuff indeed. Not too shabby at all considering Dr. Fredrick Mann was a surgeon of great esteem who just liked to shoot rifles and learn why their bullets went where they did. The copy I have contains notes written by Harry Pope; famous barrel maker of the early 1900's.

As I recall a chat with Sierra's Bob Hayden some years ago that their time of flights tests past 100 yards show bullets starting through the test screens had more consistant and higher BC values as those tested in the first 100 yards. They attributed that to bullets' stabilizing better flying point on and their long axis perfectly parallel to the trajectory axis compared to those at shorter ranges didn't fly so well stabilized. But their tests also show that even the best bullets' tiny unbalance still cause a BC spread of 1% or thereabouts.
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Old December 30, 2012, 06:48 PM   #16
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Bart, the book by Dr Mann is just awesome, thanks for sharing.
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Old December 30, 2012, 10:51 PM   #17
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"For those of you who have reloaded for a long time and shoot at different distances, will a load that works well at 100 yards typically also work well at 300 or 600 yards?"
No, but if it wont shoot at 100, it definitely wont shoot at 300 or 600.
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Old December 31, 2012, 09:18 AM   #18
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Overthere, regarding your query about short vs longer range group sizes, probably not.

Groups get larger in subtended angles as range increases. For the most part, that's caused by muzzle velocity spread.

A 50 fps muzzle velocity spread from a .308 Win. at 100 yards causes about 1/10th inch vertical shot stringing, at 200 yards about 1/4th inch and at about 3/4 inch at 300 yards. At 600 yards, it'll be 5 inches and at 1000 yards it'll be over 20 inches. That's a 1/10th MOA spread at 100, 1/4 MOA spread at 300 and a 2 MOA + spread at 1000.

So, through 300 yards, it's pretty close. As range increases, the spread gets bigger.
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Old December 31, 2012, 10:03 AM   #19
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I have never been able to get a good consistent group of 12" [kill zone sized] at 600 yards that is centered on the bullseye.
I can get that group at 500 yards if the wind is lower, with the 7mmRM.
So deer are safe with me at 600. I am not shooting.
But at 400, they are as good as dead with the 257, the 270 or 7mmRM.
I have been trying to get better for years, and progress is slow.
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Old December 31, 2012, 10:48 AM   #20
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Your eyes are the most important factor in shooting good @ 100 then @600.

Being a Diabetic my vision changes thruout the day and session.

Some days my vision is 20-20 some days are worse. With age/experience you might be a better reloader but your eyes are no longer capable to compete.

I have shot loads from my 308 using a 147 FMJ Win bullet. It stabilizes around 300 yards(2") and the 100 yard groups suck (1-2") sometimes the groups are smaller @ 300!
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Old January 1, 2013, 04:48 PM   #21
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Trajectory calculator online

If interested in external ballistics, This will give some idea of what to expect in drop at the ranges you shoot.

Plug some numbers into this site's trajectory calculator.

http://www.shooterscalculator.com/ba...tory-chart.php

You input info such as range, velocity, ballistic coefficient of the type of bullet. Manufacturers publish this on their products.

It makes a chart that graphically shows bullet path

(If you want more detail on drag coefficient shapes here is a chart or otherwise use g1.)

http://www.frfrogspad.com/drgshape.htm

I use several different bullets and this info comes in handy

According the ballistic coefficient of the bullet you are using you can get some idea of drop at different ranges.
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Old January 1, 2013, 05:00 PM   #22
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Loads that provide good groups @ 100 yds. should be good out to at least 300 yds., and usually to 500 yds. Past 500 yds., "keyholing" usually comes into play and a different bullet/load will be required. Bullet stability is the key, with bullet length being the first consideration, and bullet weight second.
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Old January 3, 2013, 06:56 AM   #23
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89blazin, rarely do bullets start keyholing past 500 yards. To date, if they're well stabilized, they'll fly point on with their long axis tangent to the trajectory axis all the way to the target as long as they remain supersonic. They'll all have a microscopic amount of coning due to the tiny amount of unbalance which causes a bit of additional drag but that's only going to cause about a 1% spread in ballistic coefficient, for the most part.

While a bullet's length, shape, diameter and weight are important, so is the rate they're spun at. Each bullet has a narrow range of rpm's that it stabilizes best at. Too fast and their slight unbalance will cause them to jump too far off the muzzle axis; too slow and they'll quickly start wobbling too much and change directions. Which is why a bullet leaving the barrel very fast can have a slower twist than one leaving slower.
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