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5-Shot Test Group's Size and Shapes

Bart B. said:
I said "most" or "some" or "up to".....

Show me where I specifically said "all groups" without any other bandwidth.
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Show us Benchrest results that support your spread input. Like what ever ones you have been basing your input from. The Cactus attachment is all computed to a "Spread" column for you to see, with all spreads of 5X and greater highlighted.
 
@Bart B.

Attaching (below) "spread data" computed from the 2017 IBS-600 Yard Nationals.

Here is stats from the "spread" data in the attachment:
  • Spread Average: 2.65 X
  • Best Spread: 1.4 X
  • Worse Spread: 6.5 X
  • Count of 5X or more: 4
From these stats, again repeats the fact that 5X and larger spreads are more of a rarity in Benchrest.
 

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Joe Salt said:
I shot a ten shot zero once at 1000 but it was 7" out of the scoring with about 30 mph wind. HA HA

Joe Salt
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Do you know what a 10 shot ZERO IS ? IF The diameter of the bullet is 243, the target has to measure 342 or LOWER to be a ZERO
 
damoncali said:
I'm not sure anyone fully understands bullet seating depth and its impact on group size. Here's what I do know and/or believe:

1) a single 5 shot group is not going to produce repeatable "group shapes". It's just not.

2) bullet dispersion is largely governed by in bore tipping of the projectile. (This much, we know is fact). This is what I believe seating depth impacts. I will admit I don't have a strong explanation as to how, and neither do I have any evidence that seating depth impacts in bore tipping, but it seems to be the most likely culprit. The other would be barrel exit timing, but the math on that is suspect. My current hand wavy hypothesis is that bullets are released asymmetrically to to case wall asymmetry and will oscillate (tip back and forth) slightly as they move towards the rifling. Once they hit the lands, they stick and that's the amount of tipping you wind up with. Certain seating depths will allow the bullet to hit the lands straighter than others due to the timing of the oscillations. Note: I made all of that up and have NO evidence that that is what actually happens.

3) It is plausible that there is a gravity dependent "orientation" to the tipping.

4) Barrel muzzle movement is not purely up/down or side/side or any clean orderly geometric shape. It's wonky. That's a scientific term for "catywompus".

5) I think a lot of load development "techniques" are really just different ways of shooting a bunch of groups and picking the best ones. Some are more orderly and logical than others. But there's a whole lot that don't make any sense at all, and yet still work, just because people keep shooting until they find their tune.

Personally, this is one of the great mysteries of internal ballistics - the question "why does seating depth have such a pronounced impact on group size"?
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Bullet Tipping: Traveling down the bore is the final bullet swagging operation??? The bore might straighten out the wobble???
 
The World record group at 100 yards is held by Mac McMillan ( The Rifle company, That how he got the start) 5 shots that measured .009 @100 yards in a 25 MPH push.
 
damoncali said: ↑

Personally, this is one of the great mysteries of internal ballistics - the question "why does seating depth have such a pronounced impact on group size"?

Harmonics
 
Bart B. said:
For those who don't understand, or realize, or comprehend that "up to a 6X spread" includes a 1.001 X spread and all other increments of any multiple up to and including a 6.000 X spread, I cannot help you grasp reality.
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Oh. Then you perhaps might have asserted, just as confidently, say "up to a 20x spread." Heck, occasionally someone misses a backer entirely. "Up to an infinite spread"? How can you ever be wrong?
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brians356 said:
Oh. Then you perhaps might have asserted, just as confidently, say "up to a 20x spread." Heck, occasionally someone misses a backer entirely. "Up to an infinite spread"? How can you ever be wrong?
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Click to expand...

I've seen some competitors get 10x spread and more. he had that one covered.
 
brians356 said:
Good to know, thanks. But, what does the distribution curve between 1.001x and 10x look like?
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Never really thought about it. Ive never heard of anybody looking at the spreads of the bottom half of the lineup until now. Its gotta be a nice looking curve though.
 
@Bart B.

Attaching (below) 2016 IBS-1000 Yard Nationals computed "spread data".

Stats from the "spread" data in the attachment:
  • Spread Average: 1.63 X
  • Best Spread: 1.01 X
  • Worse Spread: 3.97 X
From these stats, again repeats the fact that 5X and larger spreads are more of a rarity in Benchrest.
 

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