same size groups at 250 as 100?!

[car15bill]

I have been looking to see what my 225 winchester will do with some different handloads using 55grn soft points. It seems to be shooting well with 36 grains of H380, making 3 shot groups within 1 inch pretty common, and if I shoot 5 shot groups, I usually get a flyer or 2 that streches the group out to 1.5 inches.

However, yesterday I wanted to stretch it out a little more to 250 yards. I wasn't even trying that hard, and i put 2 groups into 2 inches at 250 yards.

Shouldn't I be shooting smaller groups at 100 yards if i can get that at 250?
Do some bullets stabilize at longer ranges?

 

[Uncle Mike]

Shouldn't I be shooting smaller groups at 100 yards if i can get that at 250?

Not necessarily.... bullet flight does not mimic a funnel, groups do not have to get bigger, as the rule, the longer the range.

Do some bullets stabilize at longer ranges?

Some bullets will require a longer distance to fully stabilize than other bullets, some will stabilize and then become destabilized, and later, stabilize again.... which I'll not go into, sans the long windiness of it all!

It is possible to shoot a 1" group at 100y and 200y and as the projectile slows further out...all hell breaks loose and you may get a 4" group at 300y...hypothetically speaking of course!

 

[taliv]

happens to me all the time. i seem to shoot best around 400 yrds. 1-1.5" group are pretty common for me there. however, it's rare for me to get less than 1" group at 100 yrds.

 

[car15bill]

oh ok, I was under the impression that flight did mimic a funnel, and that it was an odd problem.

 

[Offfhand]

Quote from above:

"Some bullets will require a longer distance to fully stabilize than other bullets, some will stabilize and then become destabilized, and later, stabilize again.... which I'll not go into, sans the long windiness of it all!"

wow! This is facinating. Does it mean my rifle might actually be more accurate at 200 yards than at 100? I'll post it over at the benchrest.com forum and see what they say there.

 

[Runningman]

Some longer bullets in some rifles combinations don't "go to sleep" in 100 yards. For instance I have a load in my 7mm STW with 160 grain bullet that does around 1.125 - 1.250 groups at 100 yards. It will also repeatedly shoot 1.1" groups at 200 yards! Had similar experiences with 175 grain bullets in this rifle.

 

[Offfhand]

When rifles or ammo shoot smaller groups at 200 yards than 100 yards, as described by Runningman (above) could this be called a "reverse funnel" effect? Really like to learn more about it.

 

[Welding Rod]

What you mention is not uncommon. I think I shoot better in MOA at 200 yards than at 100 yards with every long gun I own. However IMO the most likely reason is the eyes' inability to perceive cross hairs located perfectly on a target.

Lets say your perception of perfectly located cross hairs results when the hairs are within 1/8" of exact center of a target at 100 yards. All other factors aside, your inability to percieve a perfect sight picture will induce an error of approximately 1/4" at 100 yards.

Now go to 200 yards. Assuming magnification to still see the target adequately, your inabiltiy to percieve a perfect sight picture on the target is unchanged and still induces only ~ 1/4" of error on the target (not MOA).

Also, consider this. Could you shoot a tighter MOA group on 10' x 10' solid white target at 100 yards? Or on a 1" x 1" solid white target? Again the answer relates to your ability to percieve the cross hairs accurately located on the center of the target.

Now move the 10' x 10' target to 500 yards. Assuming an accurate gun, your groups may be better in MOA simply due to less % of error resulting from your inability to percieve the center of the target.

Hence the expression "Aim small to shoot small".

 

[taliv]

fwiw, i'm not claiming any sort of mystical suspension of the laws of math or physics
i think it's mostly just an 'aim small/miss small' deal in conjunction with the way i have my rifles set up, and beyond 400, the wind starts opening the groups up a bit more for me.

i don't know if i buy the sleeping bullet theory. it seems plausible to an amateur (me)

 

[Walkalong]

Shouldn't I be shooting smaller groups at 100 yards if i can get that at 250?

Yes

Some bullets in some instances take longer to stabilize than others, depending on bullet weight, twist rate, and velocity, but not more than 100 yards.

I used to prefer shooting 200 vs 100, since I seemed to do better at 200, but I just had to learn to shoot better at 100 is all. I still liked shooting 200 better, but learned to be more competitive at 100.

 

[Walkalong]

Some longer bullets in some rifles combinations don't "go to sleep" in 100 yards. For instance I have a load in my 7mm STW with 160 grain bullet that does around 1.125 - 1.250 groups at 100 yards. It will also repeatedly shoot 1.1" groups at 200 yards! Had similar experiences with 175 grain bullets in this rifle.

I may stand corrected with long range stuff. I haven't shot any of the heavy long range stuff.

But for general shooting the caliber and bullet weight he is using, I just don't see it not being stable well before 100 yards. I would like to hear from the long range guys on that.

Of course one more thing to consider is twist rate vs velocity. A bullet can be way over spun and then it will take longer to stabilize.

 

[Runningman]

The more I think about car15bill question. I got to wonder if there is a Parallax issue with this particular set up? Since long bullets and faster twist are not really a factor here.

For those that are interested Speer #14 page 418 under lab notes might be interesting to read for some.

 

[jmr40]

Smaller groups at 200 than 100 should not be happening. Smaller MOA is a not uncommon at all. If you are shooting 1.5" groups at 100 and 1" groups at 200 on a regular basis I would say something is wrong. It could happen as a fluke on rare occasions, but not all the time.

I have seen quite a few rifles and loads that might struggle to keep 3 shots into 1-1.5" at 100 yards and consistently but 3 well under 2" at 200 however. I cannot say for sure why, and suspect there are several reasons. I think part of it has something to do with bullets becoming more stable after a certain range.

I have no proof but think velocity has something to do with it. Most really accurate loads are usually not the fastest. I think that bullets that start out fast become more stable as they slow down, at least to a point. If they are too slow they become unstable once again. Bear in mind this is just my theory, I am not stating this as fact.

 

[Jim Watson]

While I know that a bullet's yaw as it exits the muzzle will damp out as it travels, there is no restoring force moving it back towards the line of travel of other bullets fired in the same direction. I do not credit the story of the "sleepy bullet." Welding Rod's theory makes more sense to me.

There was a guy on the benchrest board that set one of the Oehler Accoustic Targets up at 100 yards and a paper target at 340 yards so he could group THE SAME BULLETS at two ranges. He said that no caliber, load, or bullet he shot EVER gave a group smaller in terms of MOA at 340 yards than at 100 yards. Obviously he could not shoot them all, but he shot enough to confirm my understanding of the ballistics. I know that I have not had the "sleepy bullet" experience myself. I am darned glad to be able to hold the same MOA as the range increases.

 

[car15bill]

well this is all very interesting! im glad to know that i SHOULD be making smaller groups at 100. I'm using a bushnell banner 6x18x50 AO scope, and some cheapo no name sandbags.

when i was shooting at 100, i dont even have to walk downrange to see where i hit, which i like. however, at 250, i was having trouble seeing the target at all, i think because i did not adjust the objective lens.

On the "aim small, miss small" concept, that is why i like the 18x, but at the same time, i have a hard time squeezing off a shot because even with sandbags, there is a lot of movement. Should i be cranking it back to like 6 or 9x for 100?

 

[jmr40]

There was a rather long thread over on the Firing Line about this a couple of months back. Went about 10 pages and there is a lot of interesting info there if someone wanted to do a search.

The "aim small miss small" theory probably does explain a lot of this. But it has happened to me too many times and to a lot of shooters better than myself to completely discount. The discussion on the Firing Line pretty much ended when someone dug up some high speed photo's of the same bullet at different ranges showing that it had indeed stabilized better at longer ranges. I'm not sure everyone was convinced.

I cannot provide concrete evidence, but certainly believe there is more to this than simply aiming more carefully at longer ranges.

 

[car15bill]

someone mentioned paralax, could it have something to do with my scope and the magnification im using?

 

[Runningman]

While I know that a bullet's yaw as it exits the muzzle will damp out as it travels, there is no restoring force moving it back towards the line of travel of other bullets fired in the same direction.

Wouldn't bullet spin be considered a "restoring force".

Looking at it another way. If a bullet yaws as it exit the muzzle (they do) than dampen out as it travels down range some force is at work. At what range down range does the damping effect occur, 25, 50, 125 yards?

 

[Leaky Waders]

Hmmm...I've tried to post on this thread 3 times - maybe the server will take this one.

What I think is happening is simi;arr to W.R. - at closer targets with higher magnification, the shooter is probably chasing the bullseye. All movements as well as the target are magnified. At longer targets with the same magnification, the target and movements appear smaller, making it easier to repeat shots with similar accuracy.

For example, stand one foot in front of a wall and throw a baseball - you will hit the wall. Now back up six feet and throw the baseball, you will tend to hit the wall with the baseball at a more specific point. Your inherint accuracy never reall changed, just the perspective of the optics involved.

The real way to test these miracle rifles would be to put them in an immovable vise and shoot them.

L.W.

 

[Ky Larry]

I have a Savage Model-12BVSS in .243 Win with a Nikon 5.5-16.5X44 A.O. scope.From a bench, off sand bags, I seem to be able to shoot 100gr bullets better at 200yds and 55gr bullets better at 100yrds. I always assumed it was because of the distance needed to stabilize the bullets due to length, weight,twist rate, and velocity. Thanks for posting this info. Sounds like I need to do some reloading and range testing.

 

[Jim Watson]

Wouldn't bullet spin be considered a "restoring force".

Looking at it another way. If a bullet yaws as it exit the muzzle (they do) than dampen out as it travels down range some force is at work. At what range down range does the damping effect occur, 25, 50, 125 yards?

I don't think so. As I recall - and I am a long way from my books - the yaw damps out over distances better given in feet than yards.

Look at a hypothetical rifle fired through that guy's Accoustic Target - which plots the location of the bullet without contact and no possibility of disturbing its flight - and on to a paper target at longer range. Let's say you have a consistent .6 MOA rifle, not too hard these days, and get a slightly vertical group on the computer at 100. One wide shot is .3" above the center of the group and the other is .3" below the center. I can visualize no restoring force that will pilot the high bullet lower as it moves toward the 200 yard target and the low bullet higher as it goes that way. I think they will continue in their trajectories and hit .6" high and low, respectively, at 200; giving a 1.2" group... if nothing happens to spread it more.

Long range shooters see their groups increasing like a trumpet bell, faster than the geometric MOA dispersion will account for. The wind is the big actor, it is a lot harder to shoot MOA at 1000 yards than it is at 100, or even 500.

 

[taliv]

another thing that affects my groups is position. just so happens when i shoot 100 yrd, it's at 2 different ranges and both of them use benches. when i shoot 200 and beyond, it's almost always prone. i shoot much better prone than i do sitting.

 

[MachIVshooter]

On the "aim small, miss small" concept, that is why i like the 18x, but at the same time, i have a hard time squeezing off a shot because even with sandbags, there is a lot of movement.

I think you've answered your own question here, with a little help from Leaky Waders:

at closer targets with higher magnification, the shooter is probably chasing the bullseye.

Try turning the magnification down to 10 or so at 100. I suspect your accuracy issue is a psychological one, caused by the amplified perception of movement of the crosshairs on the target at high magnification. Could be Parallax, too. The Banners aren't particularly good scopes.

 

[Offfhand]

I put the question about a "restoring force" inproving accuracy on the benchrest forum and had a few responses. One guy gave a very knowledgable explaination of the trumpet bell effect of how group sizes expand as range increases. And how there can be no exceptions except by accident. Some of the other responders though I must be kidding to ask such a question and offered some funny explainations, wish I had saved them but my question and the answers were booted because forum manager though I was not serious by asking such a silly question.

 

[Runningman]

One guy gave a very knowledgable explaination of the trumpet bell effect of how group sizes expand as range increases. And how there can be no exceptions except by accident.

That statement does not seem agree with what Speer's professional lab technician has to say on the subject.