Is this an accuracy indicator?

[miningshawn]

I used the search to try and find some information but I don't know if I am putting in the right phrases/words.

As I have been working up various 223 loads over the last few weeks I have noticed a trend appear that occurs around nodal points. When no other parameters change, (no scope, wind, parallax, rest, etc...) a sinusoidal curve appears with changing powder weight. When the center of the curve is plotted nodal points occur when the grouping is the most "square" at or near the top of the curve.

Again, this requires that no changes happen for the entire series. It has happened with every one of the 4 load developments this week.

I am beginning to postulate a theory that this may be an indicatory test that could be applied using OCW methods, (100 or 200 yard OCW target and ladder methodology), when working up a larger cartridge. I have been stalling on a .300 Win test just because the thought of lighting off 50 full-house loads of H1000/210gr is not my idea of fun.

I would like your thoughts on this. I haven't really applied it with a standard scientific standards test, hence the sloppiness of the attached target. It is something that has just occurred to me that I am sure plenty of the more experienced shooters on this site have already noted and discussed.

On a closing note, to get on paper is a run of XM193 at the left, it looks like this rifle shoots that at or near the vary bottom of the sinusoidal curve, the vertical dispersion vs horizontal is very clear.

 

[ballisticxlr]

Plot the curve above against the waveform defined by total vertical dispersion and total horizontal dispersion within each group. My quick rough look at it without actually measuring anything, I see a definite pattern in that the high nodes appear to also be those with the least dispersion in vertical by a ways and possibly in horizontal by a bit.

 

[miningshawn]

Plot the curve above against the waveform defined by total vertical dispersion and total horizontal dispersion within each group. My quick rough look at it without actually measuring anything, I see a definite pattern in that the high nodes appear to also be those with the least dispersion in vertical by a ways and possibly in horizontal by a bit.

Thank you! This is the joggle I needed. What if I plot the vertical, then the horizontal, then compare the two curves for intersecting points? I would have to use Excel; or, could bring the results to work and use MatLab. Or both.

If I can carve out the time tomorrow and the weather isn't total crap I will get preliminary results using these and plot them.



I can keep it together much easier over 15 shots vs 65. Now the question is what distance. I am leaning towards 200 yards on this one to keep the placements tight enough to remain on one board, but also exaggerate the curve.

Thanks again!

 

[Rsadams]

100 yards is a start , as you move further out it will show you alot more.. You didn't say what distance you are going to shoot... I would refine the load as close to that distance as possible.... That's alot of shots , I would definitely clean and start over on what you have found out.. I find that after a long day I get tired and sloppy and it shows in my groups.... I test till I get tired and then stop....

 

[Evan]

I think you could do 3 shot groups and retain all the information you need.

 

[miningshawn]

So, for the 3 people watching I decided to try the theory, attached is the results. The wind was 15-20 steady and gusting to 30 but it was directly behind me. Shot 2 foulers @ 78gr. Held the same point of impact for all shots, no adjustments to the scope or Kentucky windage was applied.



When the results are graphed they look like this.


And just because I had 3 more foulers close to where those values diverge...



I wish I had chosen 78.2gr for foulers.

Or this might all be garbage.

 

[Shinbone]

Sorry, and maybe it is just me, but I am not seeing a pattern in the data.

 

[Rsadams]

To me foulers are foulers because your simply trying to foul the barrel..... What caliber are you using.? Using that much powder.. I ask because the barrel is going to heat up real fast... I zoomed in on your pictures and if it's a 300 win mag shooting under 3/4 of an inch with a factory barrel , there's not a thing in my opinion wrong with that....

Last week I watched a guy fire two boxes of 7mm mag through a factory gun pretty much as fast as he could.... The barrel was so darn hot you could feel it with your hand 5 inches above it.... That's not good either for accuracy or the barrel... The only thing he learned was how hot a barrel gets when you do that.... I just watched , it wasn't pretty...

If that's the load you want to try , try moving it out to 300 , take your time and see what you come up with and if your happy... Remember that kind of wind will definitely effect the bullet during flight , maybe a calmer day would help even more...

 

[Webster]

Sorry, and maybe it is just me, but I am not seeing a pattern in the data.

Enough flyers to indicate it's you. Not in the same direction (wind). Never shot single shots at many bulls makes it hard to interpret. . A ladder test on one bull. I have a target on the bench and mark it's hit, 1, 2, 3 ect. If it's a 300 Win Mag factory rifle mayby you should be happy with a .75" group.)

 

[ballisticxlr]

OP, can you give me the following data please? I'll work at it a bit and see if we can glean some useful info by comparing inside each set of data and between sets of data. It's best if it's formatted into columnar data but however it's easy for you is fine.

For the groups:
Group extreme spread vertical
Group extreme spread horizontal
Group vertical distance from POA
Group horizontal distance from POA
Average windage during string.

For each single shot, just put the numbers you have (include the directionality) in digital form so I can copy/paste.

 

[miningshawn]

To me foulers are foulers because your simply trying to foul the barrel..... What caliber are you using.? Using that much powder.. I ask because the barrel is going to heat up real fast... I zoomed in on your pictures and if it's a 300 win mag shooting under 3/4 of an inch with a factory barrel , there's not a thing in my opinion wrong with that....

Last week I watched a guy fire two boxes of 7mm mag through a factory gun pretty much as fast as he could.... The barrel was so darn hot you could feel it with your hand 5 inches above it.... That's not good either for accuracy or the barrel... The only thing he learned was how hot a barrel gets when you do that.... I just watched , it wasn't pretty...

If that's the load you want to try , try moving it out to 300 , take your time and see what you come up with and if your happy... Remember that kind of wind will definitely effect the bullet during flight , maybe a calmer day would help even more...

Yes, it is a 300 Win, using Berger 210VLD's and H1000.

Unfortunately I have to go to work for a couple of weeks, so even though conditions were not ideal yesterday I wanted to try this. The wind was stiff but steady at or very near 180 degrees.

Qhen I say "foulers" I normally load 5 extra near the most commonly mentioned stable loads. I use exactly the same methods to load as the rest of the test - neck turning, micrometer ogive seating, trickle powder measurement, case weight, etc... I just happened to have 3 near the weight that I suspected to show good accuracy and finished up that group.

I shot in 2 minute intervals to avoid overheating. I shot from a front and rear bag and tried my best to reduce any variables to the system other than powder charge.

I chose 100 yards solely because of the wind. There is a 500 meter and 600 yard range available and I will try one of these on the next trip home.

I am looking at this as a ladder test, plus. Why observe only the elevation value when there may be a concurrent and useful windage value at the cost of a little math? Plotting the two curves shows a divergence in waveform near 78.2gr (smoothest divergence) and 80.3gr (similar but with less width).

80.3gr of H1000 is a stout load, well above max, so I will focus near the 78.2gr node and look forward to a very low wind day and try a couple of tenths to either side. I am also willing to bet that 79.2gr is a scatter node and produces horrible groups if this methodology is correct. I will shoot a string of 3 just to confirm.

Thanks for the reply! I do appreciate your input.