Strange Grouping....

Comil_1983 said:
The little video at the end of the page from that second link is a great visual reference! So It is possible and We are not crazy. I think my brother will be working up his new loads at 200 yrds now.
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Well, you might be crazy. I don't know. Just remember his findings did not in his opinion support that particular theory being the main cause of what people are seeing.
Perhaps you can take out the uncontrolled variables and finally put the whole thing 'to rest' with a real world test of your own....
Lock the rifle in a rest, use an adjustable paralax scope, use an appropriately scaled target, shoot a paycheques worth of five(ten?) shot groups randomly between the two distances etc etc and let us know how it goes :)
I've personally never experienced this problem, but for the people who have experienced this phenomena and go with the paralax theory, have you ever 'remedied' the problem with just an adjustable scope? And by remedied I mean measureably and consistently and most importantly... completely? I definitely think its one of the more plausable explainations, but I'll bet there's a lot of br guys with adj/px scopes who still claim it. Perhaps its a part of the problem, but not the whole explaination.
I also think any such experiment should include scaled targets, and am not sure why it doesn't come up more often. I use the same targets I designed with .25" squares and darker 1" squares and a double bullseye and heavier crosshair design to sight for 25 yards (airgun) or for 225 yards (squirrel gun), but rarely if I want to do a comparison out to 400 yards with the same rifle. A scaled target gives you the same sight picture, which seems to me a fairly important thing.
Anyways, I kind of like the 'people try harder at longer distances' theory right now:p
 
As I said, The two rifles we were shooting have Identical optics, virtually brand new bought from the same store last Christmas. I would think if parralax was the issue both rifles would show similar tendancies.
 
Comil_1983 said:
As I said, The two rifles we were shooting have Identical optics, virtually brand new bought from the same store last Christmas. I would think if parralax was the issue both rifles would show similar tendancies.
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Why would you think that? Besides, parallax is so easy to check that there's nothing to think about.
 
Comil_1983 said:
So how do you check the parralax to verify that it is or is not the problem?
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Set-up on the bench, with the rifle supported front and rear. Put the crosshairs on your target, then without even touching the rifle move your head around while looking through the scope. The crosshairs shouldn't move relative to target, or just a tiny amount because there is a certain amount of compromise built into optics. They can only be perfect at one distance, and is there's problems may not be statioary at any distance.
If you can move the crosshairs around by moveing your head accuracy is only as good as your cheek-weld.
 
"If a bullet is not on line to a target at 100M, it will not "steer" itself back on course. PERIOD. Bullets just can't do that! There may be some miniscule affect caused IF the bullet has yaw...but not enough that you could possibly notice it between 100 and 200M.
2MOA @100M cannot become 1MOA @ 200M.

Yes, groups can get smaller in terms of MOA at longer ranges. happens all the time, and it is easy to see if you know what to look for. That said, I doubt it would happen at 100 to 200 yards.

I am referring to compensation. I asked about the shape of your group. If it is tall and skinny, the barrel might have a lot of compensation. barrels whip up and down as they are shot. So a fast vs slow bullet exits the muzzle aimed at a different place. "positive compensation' refers to barrels that are moving upwards as the bullet exists. A slow bullet will be aimed a bit higher than a faster bullet. At short rnage this shows up as a vertical group. 3" at 100 would be quite normal. That is a 3 MOA group. But as we go down range, those slower bullets fall a bit more than the faster ones, and the group gets flatter. At some distance they shoot to the same place, and a 1 MOA group is quite possible.

The group is bigger in inches than at 100, but smaller in MOA.

At 100 or 200, as you shoot various loads, don't touch your leveation knob. At home measure your group sizes, as normal, but also note the relationship of the group to the aiming mark. If the hotter loads shoot a bit lower, or to the same place, you have a positive compensation, and that rifle will do well at longer ranges.

But, the only explanation I can thnk of for this difference between 100 and 200 is a simple scope that lacks parallax adjustment.

Are you checking the paralax at each distance? With the rifle sandbagged, front and rear, with your cheek not touching the scope, move your head left and right. Does the cross hair move on the target? If it does, your group will be that much bigger. This parallax must be dialed out of the scope at each distance. This is what the AO is for. And dial it out by eye - not by reading the parallax scale. The scale often/usually does not reflect reality.

Hunting scopes are not much good for shooting good groups at various distances. Fixed parallax is often set at around 125 yards. if your scopes are set to -say - 175 yards, the groups will be better at 200 than at 100.
 
Me, I'm having a hard time believing that the bullet going to sleep reduces group size from 3 MOA to 1MOA in 100 yards. Not in the world I live in.

I do understand it is "possible" that 'overstabilized' bullets take a while to settle down, and then MOA gradually decreases, making it impossible to geometrically predict absolute group size at longer ranges. But absolute group size will continue to increase down range. As in a 1 MOA load at 200 yards may become a 0.9 MOA load at 600 yards, but the 600 yard group will be 5.4 inches (approx.)

Parallax, or target dimensions/contrast/shape/color.
 
Here's my theory. The barrels on these old guns are generally somewhat corroded and pitted. The more ammo that was shot in it the better it started to group because the fouling being created tightened up the bore some and it started shooting better.
 
Smaller groups at longer ranges

Theory is one thing, actual perfomance on the range is another. According to theory, smaller groups at longer ranges should not be possible, but may riflemen over the years have documented just such a thing.

I have an inexpensive Stevens 200 in .223 calibre that does this quite often. I use a 60 grain Hornady SP bullet, and with a good day, it will shoot 9/16 to 3/4 inch groups at 100 yards. At 200 yards, it averages 1 1/2 inch groups.
BUT IT ALSO AVERAGES 1 1/2 INCH GROUPS AT 300 YARDS. At 400 yards, it stretches out to 4 inch groups.

Now, why would a rifle give the same diameter groups at 200 yards, and also at 300 yards?

If you take it in MOA, then the 100 and 200 yard groups are reasonable, but the 300 yard group is smaller in MOA and the 400 yard group is slightly larger.

This is not a "one time occurance", as I have repeated it at least eight times when we get a rare no wind Manitoba day.

The Parallax idea has merit. Generally, hunting scopes are set for 200 yards, while .22 scopes are set for 100 yards.

Also, you are using two different rifles, and the rifling is different even though they may be manufactured by the same maker, one right after the other. We tend to think that each rifle is made by progression, that is a receiver is followed by the next receiver made, and the same for barrels.

It is more chance that there is a large quantity of receivers and barrels available, and in the factory someone grabs a receiver out of a bin, and a barrel from a rack, then mates them together. If a barrel, for example, was made on one day, and was put into a FULL rack horizontally, on the top row of the rack and taken for assembly, then it would be used first. If the next barrel made from the machine was then placed into a NEW rack, it would be at the bottom of the pile, and there could be 50 or so barrels between when the first one was used and the second one.

The serial number is then stamped on the assembled rifle, so we tend to think of the two rifles being made with parts that are made next to each other, and thus should have similar characteristics.

This is just one variable. Stocking, headspace, locking lug contact, chamber size, throating, muzzle crown, a dozen other factors also come into play.

So, to answer your question. Yes, it is possible to get smaller groups at longer distances. There are many factors involved, and whatever "theory" is provided, the actual experience and documentation is there to see.

Of course, "Theory" also says that a Bumblebee is not aerodynamically able to fly.
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Typically, as distance increases so does group size...and there is really no way of knowing what factors came into play in cases where shooters "claim" smaller long range groups. I too, have shot some 300M groups less than an inch...with the same rifle / load /scope combination that typically gives me 1/2" at 100M. Some days, the wind just blows 'em that way...or maybe it was humidity...or maybe it was shooter concentration...or maybe it was something else. I can't say why my 300M groups are sometimes better than my 100M groups, but I can say that I generally shoot better at shorter ranges because there are fewer outside factors acting on the fight of the bullet. In an earlier post, I may have used the term "theory", but the physics of bullet flight is not theory, it is proven and hence predictable. I am convinced that bullets cannot overcome the force of momentum to "steer" shemselves back on course...but if there is proof (mathematical...not an internet video!)...I am open to examining it!
Vertical stringing, as mentioned is, often related to velocity...whether it its a funtion of barrel compensation (which was well explained) or just good old gravity.
Please be gentle with me
 
Yeah, I'd say parallax for sure, especially with a non adjustable moderate quality scope like a Burris.
 
"If a bullet is not on line to a target at 100M, it will not "steer" itself back on course. PERIOD. Bullets just can't do that! There may be some miniscule affect caused IF the bullet has yaw...but not enough that you could possibly notice it between 100 and 200M.
2MOA @100M cannot become 1MOA @ 200M.
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Absolutely correct.
 
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