Seeking wisdom

[bsl135]

Therefore slower bullets will be deflected a smaller amount, while faster bullets will be deflected more. So there will be more Coriolis Effect at 100 yards and less at 200 yards as velocity decreases.

Please don't take offense, but this is not true at all.

The Coriolis 'effect' is an acceleration. The amount of bullet drift due to Coreolis, or any other acceleration depends on time of flight. The more time something accelerates, the faster it moves and the further it diverges from it's original path. Therefore, faster bullets are deflected less than slower bullets by a constant acceleration.

The Coreolis effect is not even relevant to the current discussion about groups of bullets since it's equal for every shot fired at the same latitude in the same direction.

-Bryan

 

[alinwa]

GARMASTERS,

And how does this pseudo-force based solely on frame of reference affect dispersion? And how do the slower bullets show less deflection? I'm honestly confused by your post, It looks like a cite but one I'm not familiar with it so can't check it for frame of reference.

What are you saying?



al

 

[alinwa]

BRYAN!!!! YOU DID IT AGAIN!!!


I thought you were in BED man!


Again, you posted whilst I wrote, sorry!


al

 

[Lynn]

Alinwa

Tell your friend with the water pipe that if he left the path open instead of using the pipe the water would run downhill without any problems.If you ever get to the Tehachapi Mountains in Southern California stop at the Edmonston Pumping Plant for a tour.They pump the water for the aqueduct and the motors are rated at something like 1,100,000 horsepower.
Oh yeah if you shoot a tracer in a 50 bmg that starts out at 647 grains it will lose 300 plus grains during its time of flight.At 1000 yards it flies like any bullet does.At 2200 yards the path is a slow clockwise corkscrew until it lines up with the target then a long straight drop.The path appears the same in the calm as it does in windy conditions even though the point of impact is different.
Lynn

 

[Sonof A. Gunn]

Amazing how this silly argument has come up again and especially that NO one has taken the time to do some basic, simple tests* to contribute verifiable results for all to see and maybe hopefully settle this.

No one seems (unless I missed it wading thru all the "bull-istics theorizing") to have mentioned what may very well be the causative factor in the instances where group size has (apparently) improved over longer distances - parallax error. IOW, the optics were adjusted for correct parallax at the longer ranges, but INcorrectly adjusted (parallax error) at the shorter range - very common error especially among novice target shooters.

*All that has to be done is to set up multiple aligned targets at several ranges and fire groups (at least 5 shots; more better) thru them simultaneously so bullets print on all targets. This should be done under no wind conditions (or in a tunnel or warehouse) and could be done with assorted guns/calibers for a variety of results.

Especially interesting would be to use a rail gun which would eliminate any human or parallax error.

Come on, somebody here ought to be able to do this and post results w/group images for all to see. One day or an afternoon is all it should take. Anyone?

Of course, as one has posted, the NRA and military has done this. How about a link to the info?

 

[BJS6]

In terms of the vertical dispersion only, I have certainly heard about a certain combination of load and rifle in the old British SMLE that would show a reduced vertical MOA spread at long range than at short. The theory was that the barrel vibration pattern with that load was such that the slower rounds left the muzzle with the barrel pointing higher than the faster rounds and thus had a self compensating effect for the velocity variation.

I am sure Varmint Al demonstrated the same thing with his 6PPC modelling. It was possible to tune the load to the barrel exit point such that the slower rounds pointed slightly higher on the target and thus compensated for the added drop of the lower velocity.

I know my BR rifle shoots higher with a 28.8 grain load than it does with a 30.0 grain load even though the two group about the same. If I was to shoot a composite group with 5 rounds of each load the group at 100 would be something like a 0.7 with two distinct clusters. If I shot the same 10 rounds at 200 or 300 isn't it possible that the higher point of impact with the slower rounds at 100 yards would compensate for the added drop of the slower rounds at longer range and thus the MOA measure of the overall group would in fact be less ?? Maybe not 200 or 300 but there must be some specific distance where the higher point of impact at 100 yards would offset the added drop and the two groups would converge and make one group smaller in MOA measure than at 100 yards ??? That of course is an extreme case but I'd imagine the same thing is entirley possible with a normal load variation, the barrel vibration and point at bullet exit relating favourably with the velocity variations so that the vertical MOA is less at certain ranges than others.

 

[J. Valentine]

Amazing how this silly argument has come up again and especially that NO one has taken the time to do some basic, simple tests* to contribute verifiable results for all to see and maybe hopefully settle this.

No one seems (unless I missed it wading thru all the "bull-istics theorizing") to have mentioned what may very well be the causative factor in the instances where group size has (apparently) improved over longer distances - parallax error. IOW, the optics were adjusted for correct parallax at the longer ranges, but INcorrectly adjusted (parallax error) at the shorter range - very common error especially among novice target shooters.

*All that has to be done is to set up multiple aligned targets at several ranges and fire groups (at least 5 shots; more better) thru them simultaneously so bullets print on all targets. This should be done under no wind conditions (or in a tunnel or warehouse) and could be done with assorted guns/calibers for a variety of results.

Especially interesting would be to use a rail gun which would eliminate any human or parallax error.

Come on, somebody here ought to be able to do this and post results w/group images for all to see. One day or an afternoon is all it should take. Anyone?

Of course, as one has posted, the NRA and military has done this. How about a link to the info?

Only one problem with that is when this was supposed to have happened they used peep sights not scopes.

 

[J. Valentine]

Hi Bryan, I'm a slow typist and you slipped in while I was laboriously composing my thread.....this thread contains no references to yours.


WELCOME!!!


I'm glad to see that you're here.


Now I've got to go back and read thru start-to-finish and see how many times we've leapfrogged and inadvertantly counter-pointed in this thread....


al

Alinwa , The best way to grab your spot in the thread is quickly post a few words then reopen in edit and continue writing. That way it will reserve your spot.

 

[Lynn]

Son Of A Gun

I believe Henry Childs has done this test many times over acoustic targets like Alinwa described.The groups get larger each time but nobody here seems to believe the results once they are given.
Lynn

 

[Sonof A. Gunn]

Quote: "Only one problem with that is when this was supposed to have happened they used peep sights not scopes."


When what happened and who is "they"? Why is it a problem?

 

[alinwa]

Lynn,

Thanx for confirming that water in an open ditch will still run downhill

Sonofagun,

All of the points you mention have been addressed and documented in past. Bryan posted in this thread about parallax error and has brought it out on past discussions.

Bryce,

You must have a rifle shooting perty good if you can see the sine wave printing on your target.....good on ya!!

J. Valentine,

Thanks for the heads up. Good idea, I hadn't thought of that.


Lynnagain,


YUP, I agree that that's a problem. A whole bunch of folks are so wrapped up in wanting to believe in magic that they refuse to accept tested FACT. A quick drive through any old-town will confirm this...........look how many acupuncturists, palm-readers, naturopaths and butt-swabbers are doing booming business between the pawn shops and paycheck loan places.......OOHHhhhh, I'm sorry! "colo-rectal massage and lavage therapists"......no offense to the retentives reading


Big as life, main street downtown where I live "COLON HYDROTHERAPY and CANDLING, pets welcome!".....UN-believable!


And we wonder why folks want mystery? It's just to distract them from their private reality!!


LOL


al

 

[Sonof A. Gunn]

Sonofagun,

All of the points you mention have been addressed and documented in past. Bryan posted in this thread about parallax error and has brought it out on past discussions.


al

OK, so once again this topic is discussed to death without anybody even saying they'll go out and do some shooting to settle this one way or the other to which I say...

WTF!



Strong suggestion: Wilbur, close this thread!

 

[Lynn]

Son Of A Gun

I think what Alinwa is trying to say is its all been done before and posted here as well.
I had a gun that I thought was shooting smaller at 300 yards than at 100 yards.Henry Childs told me I was daffier than a famous duck.He told me to line up several targets so a bullet hitting the 100 yard would also go through the 200 or 300 yard target whichever distance you think is the best grouping.I pounded some rebar in the ground and wired a 2X4 to it at each distance so a target could be stapled up and the problem went away.
I also used a bullseye at 300 yards to hit a target at 100 yards and vica versa.In that situation I shoot better at 100 yards when I'm aiming at something 300 yards away.
The test is very to do if you have a portable bench.I was trying to do it at our local range and the 100 200 300 yard berms have too much elevation to make it work.You need a flatspot.
Henry has actually done this test across a pair of Oehler 43's not the much cheaper Oehler 35's and used acoustical targets as Alinwa recommended.That is exactly why he knew what I would see.
Wilbur shouldn't pull a thread unless it's somebody picking on a gunsmith.
Lynn
P.S. Now that I think about it check the 1000 yard forum.I don't think Henry would post on this one and that is probaly why it is familiar to Alinwa as he hits them all.

 

[BJS6]

Lynn,

I am not saying I disagree because I just don't know if my idea has any basis in reality, just wanting your input.

Varmint Al posted in his 6PPC barrel vibration modelling posts that you can tune the load so that the bullet exits just before or after a high or low point in the barrels vibration. Done right the slower bullets will exit when the barrel is pointing higher to offset the velocity variation.

Now I can observe a change in point of impact at 100 matres with different loads in my 6PPC. A load at 28.8 grains impacts notably higher than at 30.0 grains. If I shot loads with a wide variation of velocity, even intentionally loaded with variation in powder weights, isn't it possible that a slow load would hit high at 100 but out at some longer distance the higher barrel point along with lower velocity will result in less vertical in MOA terms at that longer distance than the same rounds would shoot at 100 metres ???

Seems perfectly logical but maybe I am missing something here.

Bryce

 

[Lynn]

Son Of A Gun

I shoot 600 and 1000 yards and use some big cases from time to time.In doing my load work-up I may start at 73 grains of powder and go past 83 grains of powder.If you go up incrementaly in say 0.5 grain jumps your target will show vertical then a flat spot that rolls off just a touch right before the shots start to climb again or go vertical.I always find my best accuracy at that point.

Occasionaly you will ge a shot that is way low for its powder charge.If a guy was to think the bullets converge farther out that is the charge I would use in my testing.

In my case I didn't think the groups were opening up in the correct MOA proportional to the distance shot.

In your example it sounds like your looking for a down range convergence using two different loads? Were one hits high and the other hits low and at some point they will meet or converge.Interestingly enough Australia's Jeff Rogers(aJR) thinks along those same lines and also posts on the 1000 yard forum.

I also was under the impression Alinwa himself thought convergence was valid?
Lynn

 

[BJS6]

Two different loads ?

Here is my scenario. At 100 metres 28.8 grains N133 and a Barts Ultra will impact something like 0.7 inches higher than the same load with 30.0 grains N133. So if I had a poor loading system and had a ten shot group with 5 each at 28.8 and 30.0 I'd have a 10 shot group with bout 0.7 of vertical and two seperate groups.

Lets assume that at 300 metres the extra elevation of the slower load compemsated for the lower velocity and increased drop. It has to be that at some stage those two set of 5 rounds would converge, it may not be 300 but at some distance they simply have to, they can't possibly not cross trajectories, can they ???

So lets assume it is at 300 metres that they cross. Both loads will shoot sub 0.20 at 100 metres but as a composite group (like might happen if the ammo was loaded poorly say) would have about 0.7 MOA vertical. At 300 metres if the trajectories converge the 10 shots are not likely to have 0.7MOA in good conditions. Logically the 10 shots at 300 would have a lower MOA spread than at 100.

Now if the loads were spread over a range of powder weights from 28.8 to 30.0 grains wouldn't the same hold true ? Each shot would have a different velocity and a different trajectory but each faster one would start off with effectively a lower elevation at 100 and less drop by that assumed 300 metres distance. The result being the same vertical spread just over a range rather than two seperate groups at 100 and still a converging of trajectories at that assumed 300 metres.

Why could the same not hold true for normal loads with some velocity spread greater than ideal that happen to coincide with the point just before or after a trough or peak in the barrel vibration depending on the velocity ??? Logically you could create a situation where you had more spread close in than out at range or more spread out at range than close in. All that you'd be doing is tuning the load to be ideal for the distance you are shooting at or for a different distance.

Will the best 1000 yard load for a 6.5-284 say always be the same as the best 100 yard load or 300 yard load ?? Couldn't some added vertical at say 300 yards actually help at 1000 yards if the higher shots were the slower shots ???

What am I missing ??? Why is that not entirely possible ???

Bryce

 

[Lynn]

Son Of A Gun

Bryce I think we are thinking the same thing on your first point.I consider 28.8 and 30.0 to be 2 different loads.
In that example like you I think they have to cross paths somewhere.
On the second part were you are staring at 28.8 and going up slowly to 30.0 I don't see what you are seeing.In my guns as you go up in powder charge you see vertical except for that one freak load which in your case would be 30.0 grains of N133 hitting lower on the target.
I have never shot that freak load as I call it.In my guns going up 0.1 grains after that freak load always goes back to being vertical with a higher impact point.
Lynn

 

[BJS6]

Lynn,

In my situation, based on a few 5 shot groups while fine tuning, as the powder weight increased the point of impact walked down the page. As I hit 29.8 grains the group was as low as it would get and at 30.0 and 30.2 grains the point of impact started to climb again. All these groups were much lower than the previous accuracy node at 28.8 grains.

It seems that if I fired groups at 0.2 grain steps from 28 to 30 plus grains on targets right beside each other I'd end up with a nice curve plotted out based on the centre of each group.

As I understand it that is the same as "Rifle accuracy facts" demonstrates with varying loads shot in a rail gun. The point of barrel exit of varying loads will alter the point of impact depending on the vibration and velocity.

While my point is purely theortical I can see that if I intentionally or otherwise loaded ammo over a small range of weights either side of 29.5 grains I could get less spread at some longer distance than at short range, in MOA terms at least.

Perhaps short stiff PPC barrels twang about differently to longer heavier barrels on 1000 yards rifles ???

Bryce

 

[bsl135]

Bryce,
The situation you describe is perfectly logical. In fact, the effect you describe is the basis for 'ladder testing' that you occasionally read about. So many people say that you must test your loads at the intended range to truly know how it will perform there.
I proposed this as a possible explanation for the non-proportional grouping when this conversation came up last year. I was told by most of the shooters who have observed the effect that the groups (big and small) were round. This kind of negates velocity and barrel vibration as the culprit. If velocity variations and barrel vibrations were to blame, the close groups would be all vertical. That's not what's observed by those who report this behavior.
The more this topic is discussed, the more I'm convinced that optics are the culprit. Lynn's experience certainly suggests optics. If nothing else, we can all have a valuable 'take away' from this discussion: check your parallax! You may actually have a world class rifle & load, but suffer loss of precision from parallax. Such a problem would be hard to discover unless you specifically look for it.

Son-of-a-gun,
You seem to be pretty upset about the lack of action on this problem. In fact, many folks have done work and posted their results. Personally, I spent 2 solid weeks of computer modeling to find out if epicyclic swerve (corkscrew flight path) was the culprit. I showed thru computer simulation (the only practical way to study epicyclic swerve) that it was not. Lynn, Donovan, Bryce and others have also shared their observations and efforts.
What contributions have you made to this study?

-Bryan

 

[BJS6]

Thanks for the extra info Bryan.

I do believe the vertical spread thing is a valid way that a group at shorter range could in fact be bigger MOA than at longer range, it could happen in certain situations.

You say that the observation was rounded groups which rules out what I was talking about as a possible solution, unless some wind was at work and added some horizontal to the vertical and made round !!

Bryce