Federal New Cartridge

[BBob]

When I punch a large SD into a WEZ calculator the hit probability goes to crap at distance. If large velocity variations are not indicative of some amount of vertical stringing...
I mean how would that be? If you're somehow perfectly zero'd at X distance at X velocity, and then the velocity drops 50fps, physics would require that shot to hit somewhere lower than the previous that was at the X velocity.

Your thinking is too narrow. You are only taking a few variables and plugging them into a calculator, not the whole system as it works in the world. Some things still cannot be totally explained by rigid math. Just because you think it's fully logical doesn't mean it is, it might mean you're missing something.

Peruse this dilemma by researching how many long range BR folks these days get better winning groups with a larger ES/SD than smaller. It is really common. Positive compensation has been suggested as a reason. It hasn't been proven but it's a theory. The single digit ES holy grail isn't what it was cracked up to be.

 

[Dos XX]

I've never shot a load with an es over 20 in competition, but I have chosen a load with an es of 16 or 17 over one with an es of 9 because it shot smaller at 1000 yds. I also won some medals with it.

I'm not saying one with es over 20 can't do it. I'm just saying I haven't personally seen one in my experiences. If I do, I will shoot it, though.

 

[BBob]

One example from a well known 1K shooter/gun builder:

"My point is guys will get on a ballistics calculator and say you need x es to shoot x vertical based on bullet drop. They ignore barrel harmonics. Theres 12 shots in 3.6 inches of vertical at 1k with 36 fps of es. 9 shots in 2 inches with 23. They will tell you that's not possible. It's very common to see if you shoot groups a lot. I try to help guys improve their accuracy and so many are focused on single digit es when they are shooting .5 moa or bigger. I dont want to hear about single digit es unless your shooting under an inch at 1k or your shooting past a mile."

Keeping it simple with reloading

More than one way to skin a cat. As long as your rounds are consistent you're doing it right IMHO. Of course what do I know. I use Lemon pledge!! LOL.

www.longrangehunting.com

 

[z987k]

Your thinking is too narrow. You are only taking a few variables and plugging them into a calculator, not the whole system as it works in the world. Some things still cannot be totally explained by rigid math. Just because you think it's fully logical doesn't mean it is, it might mean you're missing something.

Peruse this dilemma by researching how many long range BR folks these days get better winning groups with a larger ES/SD than smaller. It is really common. Positive compensation has been suggested as a reason. It hasn't been proven but it's a theory. The single digit ES holy grail isn't what it was cracked up to be.

The only way the same rifle and bullet are not shooting lower with something like 50fps less is if it's being compensated for. Physics is physics. Something slower with the same drag profile has to be lower. Something faster has to be higher.
Random dispersion due to barrel harmonics and the shooter(the largest variable) can eat into that, but if we assume a hard mounted rifle that cannot change it's point of aim, there's no way you're not going to see it drop.
I would expect the same result if I dropped the powder charge and got lower velocity. Let's take this thought experiment to it's extreme. My ES is 400fps. First shot is 2800fps. Then next is 2400fps. Then next is 2600. That's not going to have vertical stringing?

I generally don't chase SD, but I also don't hunt at ranges where larger SD's would mean I miss.

 

[Axlrod]

The only way the same rifle and bullet are not shooting lower with something like 50fps less is if it's being compensated for. Physics is physics. Something slower with the same drag profile has to be lower. Something faster has to be higher.
Random dispersion due to barrel harmonics and the shooter(the largest variable) can eat into that, but if we assume a hard mounted rifle that cannot change it's point of aim, there's no way you're not going to see it drop.
I would expect the same result if I dropped the powder charge and got lower velocity. Let's take this thought experiment to it's extreme. My ES is 400fps. First shot is 2800fps. Then next is 2400fps. Then next is 2600. That's not going to have vertical stringing?

I generally don't chase SD, but I also don't hunt at ranges where larger SD's would mean I miss.

Thought experiments are not real world, and neither is 400 fps ES. The only thing that matters is the target.

I shoot at the range, where a few 1000 yd BR guys tune, that is in @BBob's post. This is where I picked up my load development method. Those guys choose the load for target and hunting guns based on vertical , not ES.

This is from that thread post #152, it's Wheeler on ES at long range. This is stuff you can test with your own gun, without believing someone on the internet though.

Literally hundreds if not 1000s of 1000yd groups and what I posted is just what I expect to see. Its very rare to shoot the little groups with small es. The small es groups usually have too much vertical. The single digit group thats tiny at 1k is kind of rare. Dont ask me exactly why it works out this way but it does. I dont think theres anyone out there that posts as many 1000yd groups as I do. And I only post a fraction of what I shoot. Theres guys that shoot more of them then me that do not post online. We all share this stuff with each other. The data base is huge spanning well over 10 years. Its just that not many guys are doing this stuff so it seems to go against the grain of theory.

 

[solarshooter]

It is incorrect to believe that Velocity ES and SD directly correlates with vertical or group size at distance.

I believe what Form is trying to say here is that MV dispersion is only one of many variables (rifle accuracy error, aiming error, BC error, wind error, etc) that affect point of impact on target. If you disperse this effect with realistic variations on those other effects, you will not see a 1:1 change in vertical.

When I punch a large SD into a WEZ calculator the hit probability goes to crap at distance. If large velocity variations are not indicative of some amount of vertical stringing...
I mean how would that be? If you're somehow perfectly zero'd at X distance at X velocity, and then the velocity drops 50fps, physics would require that shot to hit somewhere lower than the previous that was at the X velocity.

Now that being said, a lot of people are using ES and SD interchangeably in this thread. It's very important to understand that SD has roughly 3x the effect of ES. So talking about a 30fps SD or a 30fps ES are two drastically different things - that would be like saying 90fps ES vs 30fps ES. I absolutely believe that increase an MV SD from say 10fps to 30fps will have a significant effect on hit rates at 500+yds. Perhaps you could post some WEZ runs to quantify this.

Positive compensation is an interesting theory, and Bryan Litz did some testing of it in his latest book. His conclusions were not definitive either way, but they certainly did not disprove the theory. Now, as is well known around here I am very skeptical of "anecdotes as evidence". The testimonies from the BR shooters are extremely vulnerable to small sample testing errors, confirmation bias, and many other pitfalls in data interpretation that that community is particularly prone to. Do I believe that small groups have been shot with greater than single digit MV SD? Yes. Is this proof of positive compensation? No. There are many, many other explanations for these small groups.

 

[Okie_Poke]

I should stay out of this as I'm just an armchair long-range shooter for the most part. But this is the internet, and I've read some books, blogs, and forums, so here we go.

I believe what Form is trying to say here is that MV dispersion is only one of many variables (rifle accuracy error, aiming error, BC error, wind error, etc) that affect point of impact on target. If you disperse this effect with realistic variations on those other effects, you will not see a 1:1 change in vertical.

This makes sense to me. The statement that ES and SD don't "directly correlate" with vertical dispersion at long range left me scratching my head a little bit. It seems obvious/logical that they are correlated and that vertical dispersion at range is a function of muzzle velocity consistency.

Here's a snippet from Litz making the point that muzzle velocity consistency can be more important to long range hit probability than raw dispersion in certain circumstances.




Shamelessly snipped from: https://www.facebook.com/BryanLitzB...may-be-frustrated-getting-co/505306375445571/

But I agree it's not 1:1, and there is a point of diminishing returns to muzzle velocity consistency. Where that point is will depend on several other variables including those listed and the target size.

Here's an example from Cal based on WEZ:



From: https://precisionrifleblog.com/2015/04/18/how-much-does-sd-matter/

Now that being said, a lot of people are using ES and SD interchangeably in this thread. It's very important to understand that SD has roughly 3x the effect of ES. So talking about a 30fps SD or a 30fps ES are two drastically different things - that would be like saying 90fps ES vs 30fps ES. I absolutely believe that increase an MV SD from say 10fps to 30fps will have a significant effect on hit rates at 500+yds. Perhaps you could post some WEZ runs to quantify this.

Agree with all of this. To bring this back to what started our sidequest here:

My experience with these really high performing ball powders... like leverevolution or superformance is that you will NEVER get the ES/SD needed for ethical shots at 800, let alone 1000 yards. They're great for speed, but not consistent enough for that long of range of shooting. Which mirrors what the Allterra guys were seeing.
My reloads for the 277 fury, the best SD I have for that round at higher pressures is 37(sample size 52). Run that through a WEZ and tell me you're taking a shot at even 500 yards. If I back the pressure off and use a single base stick at just over 65k, I can get great SD's around 5.

An SD of 37 based on that many shots translates to an ES of something like 110 from fastest to slowest. Assuming a 110 fps difference and using Federal's published G1 BC for the 170 TA (.646) and 3000 fps as a mid-point (so a velocity range of 2945 - 3055), velocity variability is contributing up to 3.61"/0.68MOA/0.2MIL of vertical dispersion at 500 yards. That's not a miss on big game all by itself, but it's not all by itself and it's only going to get worse the further you go out. I don't have access to the WEZ tool, but as solarshooter said, it would be interestng to see how much that affects hit probability under various scenarios at 500 yards (and further ranges).

z987k : did you run a WEZ analysis on this that you could share?

Positive compensation is an interesting theory, and Bryan Litz did some testing of it in his latest book. His conclusions were not definitive either way, but they certainly did not disprove the theory. Now, as is well known around here I am very skeptical of "anecdotes as evidence". The testimonies from the BR shooters are extremely vulnerable to small sample testing errors, confirmation bias, and many other pitfalls in data interpretation that that community is particularly prone to. Do I believe that small groups have been shot with greater than single digit MV SD? Yes. Is this proof of positive compensation? No. There are many, many other explanations for these small groups.

Agree again. Count me among the skeptics.

 

[solarshooter]

Here's a snippet from Litz making the point that muzzle velocity consistency can be more important to long range hit probability than raw dispersion in certain circumstances.

Agree with all you said. Just note that in this example Litz is purposefully using extremely tight dispersions on the other variables to exaggerate the effect of the MV SDs. As I stated, if you use more realistic (larger) dispersions on other variables the net change due to MV SD will get smaller and smaller.

 

[Formidilosus]

The problem with using the WEZ for MV SD is that it assumes that the placement of higher MV and lower MV individual shots are random. Maybe they are, maybe they aren’t.

However there are lots, and lots of rifles and loads that hold very good vertical, with very bad MV ES

The latest is this one:


This is what it did at 100 yards-









It produced a 14” group at 1,100 yards from these 8 shots- and the 2nd lowest shot on target was the highest MV.





My previous match 308 barrel and load had on average an 80fps ES over 10 shots, yet was between 6-9” of vertical for those same 10 shots at 800 yards.

ES has mattered or meant so little to actual on target group size at sub 1,000 yard range where I/we spent most of our time, that I didn’t even own or use a chrono to check loads for nearly a decade.

 

[Bugger]

The problem with using the WEZ for MV SD is that it assumes that the placement of higher MV and lower MV individual shots are random. Maybe they are, maybe they aren’t.

However there are lots, and lots of rifles and loads that hold very good vertical, with very bad MV ES

So is it just an unexplained phenomenon that due to harmonics and “barrel whip” the lower shots in the group tend to be faster and higher ones happen to be the slower shots? I knew that was a factor but didn’t think there was a pattern to it, especially a trend that would span across different individual barrels in different calibers, lengths, and profiles. One of those interesting clashes between what should and what does happen.

 

[solarshooter]

This is what it did at 100 yards

Agree that at 100yds MV SD/ES is irrelevant. Here is a 20rd group spanning 4.5gr of powder and 370fps MV:

the 2nd lowest shot on target was the highest MV

Back when I used to sweep powder to try and tune loads, I would often observe that faster loads printed lower on target, and slower load vice versa. This is at 100yds, and 5-10 shot groups. This is by no means a validation of positive compensation, but it is interesting to note. If you subscribe to barrel harmonics being a significant factor in accuracy, one explanation could be that the bullet is leaving earlier as the barrel is still swinging up in an oscillation. But, as has been thoroughly discussed and debated here, not everyone things barrel harmonics are meaningful/impactful (they are certainly real).

So @Formidilosus, the math would say your ES should produce more vertical than you saw, especially considering other sources of error. What is your best guess as to why you don't see that much vertical on target?

 

[Dos XX]

Try tuning a load with a 1.25 straight, no taper barrel, then with a Heavy Varmint, MTU or Rem Varmint barrel.

 

[rbutcher1234]

My 93 shot group that was about 0.7” was from a load with an ES of 80

 

[Formidilosus]

So @Formidilosus, the math would say your ES should produce more vertical than you saw, especially considering other sources of error. What is your best guess as to why you don't see that much vertical on target?

I don’t know for sure. And nether does anyone else that I’ve spoken to about it- lots of theories (positive compensation seems to be the consensus), but no one that I know of has rigorously tested it with high number of sample guns/loads.

I do know that it happens often enough that I don’t really care about it. I don’t really like to see 125fps ES on 10-20 rounds, but I’ve seen enough combos shoot the same MOA size or within .2 MOA; average 10-30 rounds groups at 400, 600, 800, and 900 yards as they do at 100 yards with high MV ES and SD- that I do not care what it is. If a load shots well for 10+ rounds at 100 yards, I immediately shoot it at distance- usually 970 yards currently. If the group vertical holds similar to 100 yards- it’s good.

 

[Formidilosus]

Also, the above is terminal bullet performance ranges- 800-900 yards. Dedicated long range and ELR past 1,100 to 1,200 yards I will pay attention to MV ES and SD, but will still default to what happens on target. Rarely is does the lowest MV SD load shoot the best that I’ve seen, even at 1,300 yards.

 

[solarshooter]

A few things that could be causing this observed phenomenon, coming from a purely objective Design of Experiments perspective:

• MV measurement error
• Group vertical measurement error
• Small sampling error/random chance combination of other variables
• Positive compensation
• Some other explanation?

Litz's experiment involving shoot-through targets at multiple ranges on flight path of the bullet is the best experimental design I've seen to test this phenomenon since it cancels out the effects of many variables. He also uses lab grade chronometers. We'll have to wait for his next book to come out before we know the answer.

 

[Bluefish]

So is it just an unexplained phenomenon that due to harmonics and “barrel whip” the lower shots in the group tend to be faster and higher ones happen to be the slower shots? I knew that was a factor but didn’t think there was a pattern to it, especially a trend that would span across different individual barrels in different calibers, lengths, and profiles. One of those interesting clashes between what should and what does happen.

I think the Hornady guys touched this on a podcast. Due to drag variability on bullets can cancel out or add to the variation in MV. They can see this with the radar. A fast bullet may have more drag and thus slow down more on a long shot, hitting lower than a bullet that started out slow but has less drag. They were talking about minimizing drag variation vs maximum BC. But the concept can account for why a good SD does not necessarily mean less dispersion.

 

[z987k]

I think the Hornady guys touched this on a podcast. Due to drag variability on bullets can cancel out or add to the variation in MV. They can see this with the radar. A fast bullet may have more drag and thus slow down more on a long shot, hitting lower than a bullet that started out slow but has less drag. They were talking about minimizing drag variation vs maximum BC. But the concept can account for why a good SD does not necessarily mean less dispersion.

That's the best sounding theory so far I think. I'll have to go find it and see what they're saying.

 

[z987k]

An SD of 37 based on that many shots translates to an ES of something like 110 from fastest to slowest. Assuming a 110 fps difference and using Federal's published G1 BC for the 170 TA (.646) and 3000 fps as a mid-point (so a velocity range of 2945 - 3055), velocity variability is contributing up to 3.61"/0.68MOA/0.2MIL of vertical dispersion at 500 yards. That's not a miss on big game all by itself, but it's not all by itself and it's only going to get worse the further you go out. I don't have access to the WEZ tool, but as solarshooter said, it would be interestng to see how much that affects hit probability under various scenarios at 500 yards (and further ranges).

z987k : did you run a WEZ analysis on this that you could share?

I did, and it's not the 7BC, but the 277 fury and a 150gr bullet with only a BC of .460, Avg MV 2849(short barrel), SD 37, ES 121.
I ran it again, with a 1MOA rifle, a 5mph crosswind +/-2 mph, a 2MOA target, 500yd, no BC variation, hit probability is about 45%.

 

[Okie_Poke]

I did, and it's not the 7BC, but the 277 fury and a 150gr bullet with only a BC of .460, Avg MV 2849(short barrel), SD 37, ES 121.
I ran it again, with a 1MOA rifle, a 5mph crosswind +/-2 mph, a 2MOA target, 500yd, no BC variation, hit probability is about 45%.

What happens if you drop SD/ES to 10/40 with same parameters?