Good groups @100yds.

[KY_Windage]

So a 1moa load at 100 might approach 2 moa at 200, but it won't be <2moa.

You must be thinking of inches instead of MOA. I shoot the same MOA at 100 and 200 (or real close to it) all the time.

 

[INTJ]

Typical 6mm 103-105 class bullet shooting .000" at 100 and has an extreme velocity spread of 20 fps. You've done a great job sorting and the B.C. variations of the 5 bullets is .000. My program says this would be a 4.5" vertical spread at 1,000 yards.

Can anyone explain why it is that several groups, and piles of groups with less than 2" of vertical, have been achieved at 1,000 with loads that have 15-20 fps of extreme spread? And i don't mean like once or twice a year, I mean like EVERY time conditions are half decent.....as in EVERY SINGLE TIME. Is the chronographs still no better than the old oheler? Or is something else at play? I do my tuning, because I can, at distance. Have been using a spot i can access easily at 871 yards. And just like at 1,000, the odds of shooting a poor group actually increases once my ES dips below about 5-8 fps. I see this anomaly more than once a year as well, lol....somewhere around 97.2% of the time

I think a good gun can be determined at 100, it still has to shoot and agg. I just don't know about the specific load though. Possibly competitive out to around 800ish with what I've seen on the BR based 6mms that I glean my experiences from. For sure still pretty solid at 600.


Just a couple extra penny's for everyone, since there's no damn matches yet lol

Tom

The reason I have heard is called "positive compensation". The theory is that a higher velocity bullet exits the muzzle sooner in the recoil process, so the barrel isn't pointed up quite as much. That seems very likely with a hunting rifle that recoils up off the rest, but our 17 lb BR rifles don't seem to lift under recoil. Maybe they do slightly?

 

[Hohn]

Can anyone explain why it is that several groups, and piles of groups with less than 2" of vertical, have been achieved at 1,000 with loads that have 15-20 fps of extreme spread? And i don't mean like once or twice a year, I mean like EVERY time conditions are half decent.....as in EVERY SINGLE TIME. Is the chronographs still no better than the old oheler? Or is something else at play? I do my tuning, because I can, at distance. Have been using a spot i can access easily at 871 yards. And just like at 1,000, the odds of shooting a poor group actually increases once my ES dips below about 5-8 fps. I see this anomaly more than once a year as well, lol....somewhere around 97.2% of the time



Tom

I'm a bit far from my undergrad aero engineering classes, but I'll hazard a guess or several:

1) Drag force is proportional to speed; it acts more on a faster bullet. The tendency over long range is for differences in speed from one shot to another to reduce. They will want to converge on a single speed (but don't, they just asymptotically approach it).

2) There are aerodynamic factors the calculators cannot and do not account for.

3) It's almost certain that a load development that focuses on vertical dispersion will select a load that tends to launch slower speed rounds at a higher angle of attack and faster ones at a lower angle of attack. The calculator assumes identical exactly consistent launch angle from one shot to another. But we know that barrels "whip" a tiny bit. And a load development that focuses on vertical dispersion will almost always produce a load that is departing the muzzle exactly as the barrel oscillation is causing the tip to rise slightly. Thus, those bullets that leave sooner (faster speed) are launched lower than those that leave an instant later. The Precision Rifle Blog is presently featuring an article on bullet jump in which Mark Gordon comments that some of the factory loads he's tested that have ES as bad as 40fps and 0.5gr charge variation will still hold half moa of vertical at 600y. He's even tested handloads where 14/15 rounds were within half moa of vertical despite *137fps* of ES.

Clearly the launch angle is not always the same. And thus can either make the vertical worse than calculator or much better, depending on which half of the barrel's up/down vibration you launch at.

 

[Hohn]

You must be thinking of inches instead of MOA. I shoot the same MOA at 100 and 200 (or real close to it) all the time.

Yes, thanks for catching my error. I should have said a 1moa load at 100 will be about 1moa at 200, but not less.

 

[Ccrider]

A gun has to consistently shoot small at 100 to shoot well at 600 and 1000. I do all my tuning at 100 yards, but I have a lot of experience shooting short range Benchrest.

Bart

Ok @BartsBullets since nobody ask, I will. What size group do you consider “small at 100.”
Thanks for sharing.
Charles

 

[tom]

@Hohn

I believe your #3 is what @INTJ is referring to as "positive compensation", and myself believe that to be what we're seeing "mostly". I like to just think of it as "tuning"....we use the barrel movement to work in our favor. I believe you both have described how it's possible to have a smaller MOA at a greater distance, and is why i posted the "question". At least on the vertical plane portion of the discussion.

Anyway guys,

So if I take my hypothetical example, in the atmosphere I have entered. I would need to actually make it shoot .450" of vertical at 100 yards, and be in the perfect launch angle and speed, in order to achieve my ultimate goal of a .000" at 1,000. Or i would have to somehow load to 0 ES every time, and have it tuned to shoot .000" every time.....I can't do that, I know my limitations! It's actually quite amazing anyone ever shoots a group under 3" when you factor in degradation and conditions. But yet i get upset on days i don't see any 1's...And I shoot a LOT, and see a LOT of good guns groups at matches.

Tom

 

[rsmithsr50]

excuse me...you shoot .5 inch at 600 yards ?? with a rifle that only shoots .25 inch at 100 ???

I think if you want to shoot small at longrange you need to shoot really small at short range. .25 at 100 = .5 at 600 at least that's how it always works for me. Mike

 

[KY_Windage]

excuse me...you shoot .5 inch at 600 yards ?? with a rifle that only shoots .25 inch at 100 ???

You're adding "inches" to the equation when he was talking MOA, I'm pretty sure.

 

[rardoin]

So how do the bullets forming a .7 moa group at 100 yards know which directions they need to change to in order to form .5 moa groups at 600 yards?

Magic

NOWHERE did I say it shot .5MOA at 600yds. The load did put over 50% of the shots touching a .5MOA diameter ring and the rest touching a 1MOA ring. The 10 ring is 6” at 600yds.

 

[INTJ]

.

@Hohn

I believe your #3 is what @INTJ is referring to as "positive compensation", and myself believe that to be what we're seeing "mostly". I like to just think of it as "tuning"....we use the barrel movement to work in our favor. I believe you both have described how it's possible to have a smaller MOA at a greater distance, and is why i posted the "question". At least on the vertical plane portion of the discussion.

Anyway guys,

So if I take my hypothetical example, in the atmosphere I have entered. I would need to actually make it shoot .450" of vertical at 100 yards, and be in the perfect launch angle and speed, in order to achieve my ultimate goal of a .000" at 1,000. Or i would have to somehow load to 0 ES every time, and have it tuned to shoot .000" every time.....I can't do that, I know my limitations! It's actually quite amazing anyone ever shoots a group under 3" when you factor in degradation and conditions. But yet i get upset on days i don't see any 1's...And I shoot a LOT, and see a LOT of good guns groups at matches.

Tom

Like Karl Hunstiger says, "the wind blows 'em out and the wind blows 'em in".....

 

[Evan]

Here's at 150:

Here's the same load at 350:

It HAS to shoot small at 100 to shoot small further out. But just because it shoots small at 100 doesn't mean it will shoot small further out. Here's a load that shoots small close in, but at 350 you can see the fliers:


EDIT: These are with my 22BR.

 

[Erik Cortina]

If all bullets are going through same path as defined by two points (muzzle and 100 yard target), and load has a low ES (under 20), then gun will shoot well at distance. If it doesn’t, there nothing else the rifle can do to help, so the variation must be in the bullets themselves. BC variation can cause large groups at distance even if rifle is tuned properly.

 

[KY_Windage]

Magic

NOWHERE did I say it shot .5MOA at 600yds. The load did put over 50% of the shots touching a .5MOA diameter ring and the rest touching a 1MOA ring. The 10 ring is 6” at 600yds.

Well, the difference between "touching" and "center to center" being pretty miniscule at 600 yards, you said it shot .5 MOA or real close to it 36 out of 40 times.

I don't doubt that a .7 moa rifle will sometimes shoot .4. I'm just saying it is a poor game plan to take a .7 moa rifle/ammo combination and try to hit (touch) the .5 MOA X-ring with it at 600 yards.

A vastly better plan is to start with a .25 MOA or better setup.

 

[INTJ]

@Hohn

I believe your #3 is what @INTJ is referring to as "positive compensation", and myself believe that to be what we're seeing "mostly". I like to just think of it as "tuning"....we use the barrel movement to work in our favor. I believe you both have described how it's possible to have a smaller MOA at a greater distance, and is why i posted the "question". At least on the vertical plane portion of the discussion.

Anyway guys,

So if I take my hypothetical example, in the atmosphere I have entered. I would need to actually make it shoot .450" of vertical at 100 yards, and be in the perfect launch angle and speed, in order to achieve my ultimate goal of a .000" at 1,000. Or i would have to somehow load to 0 ES every time, and have it tuned to shoot .000" every time.....I can't do that, I know my limitations! It's actually quite amazing anyone ever shoots a group under 3" when you factor in degradation and conditions. But yet i get upset on days i don't see any 1's...And I shoot a LOT, and see a LOT of good guns groups at matches.

Tom

But Tom, seriously. I know the level of tuning and experimenting you do--I live about 45 minutes from George and he's always cryptically describing what you and he are up to. So when you say you don't understand something it bothers me.............

 

[bcarico]

I do most of my testing at 100yards and my guns shoot decent at 1000yards. I have never owned a chronograph. Must be magic....

 

[Bindi2]

I start at 100 to get a reasonable tune then go to 600. The tune at 600 does not work at 1000 which also does not work at 600. So two rifles were put into play, one for the shorts and one for the longs. Having played at this for awhile I now see the case for a third rifle. One for 300 to 500, one for 500 to 700 and the other for 700 to 1000. The over lap for bigger projectiles or calibres when it is getting rough. Two calibres 7mm and 30 cal, three case sizes 7.08ai, 7.06ai and 30.06ai. 168gn, 183gn and 210gn. Single digit ES and what looks like a calibre hole at 100 but is not ( I don't measure it ) is the starting point for each. The tuners are the key.
The photo by Evan at 150 is not in tune. Which shows in the other photos.

 

[dolek]

I do most of my testing at 100yards and my guns shoot decent at 1000yards. I have never owned a chronograph. Must be magic....

Winner !!!! I like the no BS approach,well done.

 

[dolek]

I'm a bit far from my undergrad aero engineering classes, but I'll hazard a guess or several:

1) Drag force is proportional to speed; it acts more on a faster bullet. The tendency over long range is for differences in speed from one shot to another to reduce. They will want to converge on a single speed (but don't, they just asymptotically approach it).

2) There are aerodynamic factors the calculators cannot and do not account for.

3) It's almost certain that a load development that focuses on vertical dispersion will select a load that tends to launch slower speed rounds at a higher angle of attack and faster ones at a lower angle of attack. The calculator assumes identical exactly consistent launch angle from one shot to another. But we know that barrels "whip" a tiny bit. And a load development that focuses on vertical dispersion will almost always produce a load that is departing the muzzle exactly as the barrel oscillation is causing the tip to rise slightly. Thus, those bullets that leave sooner (faster speed) are launched lower than those that leave an instant later. The Precision Rifle Blog is presently featuring an article on bullet jump in which Mark Gordon comments that some of the factory loads he's tested that have ES as bad as 40fps and 0.5gr charge variation will still hold half moa of vertical at 600y. He's even tested handloads where 14/15 rounds were within half moa of vertical despite *137fps* of ES.

Clearly the launch angle is not always the same. And thus can either make the vertical worse than calculator or much better, depending on which half of the barrel's up/down vibration you launch at.

That was a long winded "Guess"...

 

[rardoin]

Well, the difference between "touching" and "center to center" being pretty miniscule at 600 yards, you said it shot .5 MOA or real close to it 36 out of 40 times.

I don't doubt that a .7 moa rifle will sometimes shoot .4. I'm just saying it is a poor game plan to take a .7 moa rifle/ammo combination and try to hit (touch) the .5 MOA X-ring with it at 600 yards.

A vastly better plan is to start with a .25 MOA or better setup.

You are correct...it was a poor game plan to not have the rifles/load developed better than what I had. But, it was what I was able to throw together with limited time and a new rifle/chambering/unfired cases. Far from ideal. A vastly better plan would have been to show up with a rifle that shot .25MOA at 600 yds.

 

[rardoin]

Hera ya go Kentucky...

This load shoots about .5-.6" at 100yds...nice round group for 5 shots (no target photos). The target below is at 600yds, same load, 10 shots/1 sighter. Tom touched on positive compensation and it is the reason I want to do final tune at the distance I will be competing at.