Where are the nodes? Data included..

[stvo6mm]

Hi all. Seeking some thoughts on where to settle my load. Cartridge is a a 300 Norma Mag, 30" barrel, Berger 30cal 220gr Long Range Hybrid Target. Powder is ADI AR2217. Seems to me to be somewhere around 83.6 gr's.

 

[MikeMcCasland]

At the risk of someone coming along and saying velocity/SD/spreadsheet flat spots are the best way to select a load, I'd encourage you to select them based on vertical flat spots on target.

IMO spreadsheets are theoretical; targets are real world application.

Do you have pictures of the target?

 

[stvo6mm]

At the risk of someone coming along and saying velocity/SD/spreadsheet flat spots are the best way to select a load, I'd encourage you to select them based on vertical flat spots on target.

IMO spreadsheets are theoretical; targets are real world application.

Do you have pictures of the target?

Wow. Thanks for the quick reply. I do, unfortunately, the rage I have regular access to is 200 yrds and at that range, they're all more or less one hole, so not much use. But attached for the record.

 

[8andbait]

I like the ring...always think there’s a flier under the coin

 

[CharlieNC]

Wow. Thanks for the quick reply. I do, unfortunately, the rage I have regular access to is 200 yrds and at that range, they're all more or less one hole, so not much use. But attached for the record.

That looks like approx 1" or 1/2moa vertical. If each load was shot on an individual target you may have well observed a harmonic pattern in poi revealing the node, which is not unusual for a group of that size.

 

[MikeMcCasland]

Again I hesitate to even post this, because there are a number of "big name" shooters that develop their loads this way. It clearly works for them given their successes, but literally every time I've tried this method I've found myself in the exact same situation you're in.

You've got a gun that looks to be shooting pretty well. No obvious flat spots with corresponding low ES/SD. You've burned up quite a few bullets that are not cheap, and now are left with no clear path forward for a load. Looks familiar lol.

I understand you're limited to 200 yards, but I think you can still acomplish testing based on vertical. I'd go re-shoot the exact same test, this time each powder charge gets it's own "target" (with all targets existing in a lateral plane). Evaluate the POI in relation to the vertical plane; when you have 2-3 consecutive charge ranges impacting in the same vertical, park your charge in the middle and go work depth.

I don't mess with the big guns too often, but at first glance it looks like you've got a well put together 300 Norma.

Maybe somebody who has lots of success with velocity/SD/chronograph load dev will come in here and set us all straight; I genuinely hope they do, because selfishly I'd love for that method to work for me.

 

[powderbrake]

I suggest you fire 3 shot groups of each loading. That way you can see the movement and location of the groups.
Here is a target that I use at 100 yards, along with a data sheet that I record the loads and the velocities. I record powder and weight, the seating depth of the bullet, the series number from my Labradar, and the velocity data. Yes , all that data is on the SD card, but I keep the data sheet with the target, and all the data is right there.

You would probably need a larger aiming point for your 200 yard range. Also , note the aiming point is off set, so I crank a couple clicks of "down" so I don't shoot into the black circle. I also use On Target software to measure the groups on the target. I then write group size and velocity on the actual targets.

As Mike McCasland said, the target will tell you which is the flat spot ( node).. Your velocity data implies 83.4 to 83.8 as the area of minimal slope, but the target will speak louder.

 

[BasicMagic]

My suggestion would be to retest centered around 84 grains. Shoot at least 3 of each charge at different targets so you can see some group size and POI shift info. Run away from 83.4 its not good.

 

[CharlieNC]

The sample size is too small to make inferences regarding significant differences in SD, and esp ES. Many on this site get tired of hearing that a working knowledge of statistics is required to determine appropriate sample sizes and methods to assess significance, but otherwise you are PIW. But a ladder test looking at your 0.2 increments across a wider range like 5gr due to the heavy charge should show a clear node at 200-300yd, and ultimately the target is the judge.

 

[Ledd Slinger]

I don’t even look at SD anymore. SDs do not determine nodes. A small SD doesn’t mean anything if the next charge with 30 fps velocity increase shoots 2 MOA higher than the last charge weight or the group is all vertical. I’ve had larger SDs shoot small and small SDs shoot big so that data means nothing to me. I will watch the chronograph for large extreme spreads in velocity because that may be a transitional point from lower to upper node or you are at max pressure

How the bullets land on paper with the same point of aim is the only thing that matters. The whole point of tuning to a node is so that if the velocity of your bullets change due to weather or other reasons while shooting, the bullets will still land in the same spot and you don’t miss your mark. Shoot a target with all the bullets on the same point of aim. At least 2 bullets per charge weight. Some folks color the bullets to see impacts on paper but I prefer mapping the impact points with a pen, paper, and spotting scope. Once you’ve found a node based on consistent point of bullet impact across varying charge weights, then shoot those groups in 3 rounds at the same point of aim to make sure it repeats. If you don’t find a node by varying charge weights alone, move on to tuning neck tension and seating depth using the best charge weight node.

FYI, the 300 Norma seems to like at least .004” neck tension and at least .020” jump with the 220gr

 

[stvo6mm]

Wanted to take the time to say thank you to all who have responded to my question. I've decided to go back shooting groups and seeing what they tell me.

 

[dcali]

These tests don't tell you anything except the relationship between velocity and charge weight. There is no such thing as a velocity flat spot. It's just statistical variation. More powder = more speed. In the narrow range we shoot in, the relationship is practically linear. (It's actually a curve that diminishes in slope as you increase the powder charge. There is no serious engineering literature describing a flat spot, and neither is there any known physical explanation for why one would exist. I know shooters swear by it, but it's just not true. It would be unlikely to create a chart like this and *not* see a flat spot, but don't fall into the trap of thinking it's anything but random.

I should throw in that they also give you a (poor) estimate of SD, which can be useful but generally won't be a "node" necessarily. In my experience, that does seem to correlate to powder charge somewhat, which can be explained by optimizing the combustion to get consistent results.

I think the misconception comes from a ladder test, which *is* legitimate. But that is a plot of velocity (not charge weight so you can eliminate variation) vs the vertical position of the impact. If you plot that, you will see multiple flat spots - a star step pattern (hence the title "ladder"). You want to aim for a velocity in the middle of one of those steps.

 

[tsmith]

I may have misunderstood what you said in your post @damoncali in your reference of more powder equaling more speed. In my test, that is not always the case. Again, I may not follow what you meant by that. As for the nodes, looking at those charts, which is out of my pay grade, I would test loads in the 83.0 to 84.6 range as that is where I see nodes on all those strings, the way I look at them. The way I load is I go out and shoot 12 rounds, increasing each load .2 in powder. I then look at the list, and find the least changes in fps, and I load there. For instance, the last test I done on my .308 gave me 2784 fps at both 44.3 and 44.5 grains of IMR4064. I also got a 5fps node at 43.3 and 43.5. I checked both these charges and found that 44.4 grains, which is where I loaded shot the best. After that, I began my seating depth test of moving the bullet in three thousands each three shot string. Out of that, I found two seating depths that shot the best. I then loaded 15 rounds for each of those seating depths and 44.4 grains to test. In the end, I found the load my rifle liked the best. This load came out with a SD of 2.8 and a ES of 7. I have tested it out to 804 yards and it's shooting .5 or better MOA with a 175SMK. Now for what this rifle will be used for, that's plenty accuracy.

 

[dcali]

I may have misunderstood what you said in your post @damoncali in your reference of more powder equaling more speed. In my test, that is not always the case. Again, I may not follow what you meant by that. As for the nodes, looking at those charts, which is out of my pay grade, I would test loads in the 83.0 to 84.6 range as that is where I see nodes on all those strings, the way I look at them. The way I load is I go out and shoot 12 rounds, increasing each load .2 in powder. I then look at the list, and find the least changes in fps, and I load there. For instance, the last test I done on my .308 gave me 2784 fps at both 44.3 and 44.5 grains of IMR4064. I also got a 5fps node at 43.3 and 43.5. I checked both these charges and found that 44.4 grains, which is where I loaded shot the best. After that, I began my seating depth test of moving the bullet in three thousands each three shot string. Out of that, I found two seating depths that shot the best. I then loaded 15 rounds for each of those seating depths and 44.4 grains to test. In the end, I found the load my rifle liked the best. This load came out with a SD of 2.8 and a ES of 7. I have tested it out to 804 yards and it's shooting .5 or better MOA with a 175SMK. Now for what this rifle will be used for, that's plenty accuracy.

No, you got me right. Powder burns and generates gas. The more powder you burn, the more gas you generate. There's no reason to believe that within sane ranges of powder charge that generating more gas would *not* generate more pressure. When you see that happening, what you're actually seeing is just coincidence. If you repeat a test many times (like 20-30 or more), you will see the flat spots go away. They are an illusion.

If you plot that same data but include error bars that cover a 90% confidence range, it will look nearly perfectly linear.

 

[CA_Shooter]

These tests don't tell you anything except the relationship between velocity and charge weight. There is no such thing as a velocity flat spot. It's just statistical variation. More powder = more speed. In the narrow range we shoot in, the relationship is practically linear. (It's actually a curve that diminishes in slope as you increase the powder charge. There is no serious engineering literature describing a flat spot, and neither is there any known physical explanation for why one would exist. I know shooters swear by it, but it's just not true. It would be unlikely to create a chart like this and *not* see a flat spot, but don't fall into the trap of thinking it's anything but random.

I should throw in that they also give you a (poor) estimate of SD, which can be useful but generally won't be a "node" necessarily. In my experience, that does seem to correlate to powder charge somewhat, which can be explained by optimizing the combustion to get consistent results.

I think the misconception comes from a ladder test, which *is* legitimate. But that is a plot of velocity (not charge weight so you can eliminate variation) vs the vertical position of the impact. If you plot that, you will see multiple flat spots - a star step pattern (hence the title "ladder"). You want to aim for a velocity in the middle of one of those steps.

Just for clarification, what you're essentially saying is:

Don't pay attention to the powder charge flat spot, but instead pay attention to the velocity flat spot.

So, for example, if 2700 to 2720 FPS gets me a vertical flat spot, then it doesn't matter what my charge is. My charge could be 41 grains today or 41.2 grains tomorrow...but as long as I'm in the 2700 to 2720 window then the charge doesn't matter?

 

[tsmith]

No, you got me right. Powder burns and generates gas. The more powder you burn, the more gas you generate. There's no reason to believe that within sane ranges of powder charge that generating more gas would *not* generate more pressure. When you see that happening, what you're actually seeing is just coincidence. If you repeat a test many times (like 20-30 or more), you will see the flat spots go away. They are an illusion.

If you plot that same data but include error bars that cover a 90% confidence range, it will look nearly perfectly linear.

I've always did my test the way I described. For me, more powder does not mean more speed in my case and the tests I've done using a Magneto V3. Here are the numbers from my last test.

42.3 - 2667
42.5 - 2662
42.7 - 2676
42.9 - 2667
43.1 - 2707
43.3 - 2703
43.5 - 2731
43.7 - 2744
43.9 - 2756
44.1 - 2762
44.3 - 2784
44.5 - 2784

I tested loads at both 43.2 and 44.4, settling on the 44.4 following seating depth test. Again, this is how I've always done my loads and I've never any issues. Now I'm sure there are better ways of doing things, and I'll admit, I'm not looking for BR accuracy as I shoot mainly steel. The above process works for me. That's why I stick with it. I don't really pay attention to the powder charge, but mainly the bullet speed. Only thing I'm concerned about on powder charge is over charging, and the casing will tell me that. I'm sure there is another node above the 44.5, but that's as fast as I wanted to run the 175SMK.

After settling on a load, it averaged out at 2768 across six shots. I took the data I got from the chrono to a distance of 804 to true MV and it ended up being 2764 once that was completed.

 

[dcali]

Just for clarification, what you're essentially saying is:

Don't pay attention to the powder charge flat spot, but instead pay attention to the velocity flat spot.

So, for example, if 2700 to 2720 FPS gets me a vertical flat spot, then it doesn't matter what my charge is. My charge could be 41 grains today or 41.2 grains tomorrow...but as long as I'm in the 2700 to 2720 window then the charge doesn't matter?

For a ladder test, yes. It's the velocity that matters. Once you know that, you want a wide window that you can take advantage of to minimize the impact of charge weight variation. Often I see people using charge weight vs vertical for a ladder test, which is kind of the same thing, but you will get much cleaner data if you just use velocity directly and then figure out what powder charge reliably gives you that velocity on average after you know what you're aiming for.

That's not to say that it's *all* that matters in the big picture, but for the purpose of maximizing the benefit of positive compensation at long range, it's what matters. Changing from 41 to 41.2 to keep the velocity constant will do this. But it might also do something undesirable. You just never know until you test.

 

[dcali]

I've always did my test the way I described. For me, more powder does not mean more speed in my case and the tests I've done using a Magneto V3. Here are the numbers from my last test.

42.3 - 2667
42.5 - 2662
42.7 - 2676
42.9 - 2667
43.1 - 2707
43.3 - 2703
43.5 - 2731
43.7 - 2744
43.9 - 2756
44.1 - 2762
44.3 - 2784
44.5 - 2784

I tested loads at both 43.2 and 44.4, settling on the 44.4 following seating depth test. Again, this is how I've always done my loads and I've never any issues. Now I'm sure there are better ways of doing things, and I'll admit, I'm not looking for BR accuracy as I shoot mainly steel. The above process works for me. That's why I stick with it. I don't really pay attention to the powder charge, but mainly the bullet speed. Only thing I'm concerned about on powder charge is over charging, and the casing will tell me that. I'm sure there is another node above the 44.5, but that's as fast as I wanted to run the 175SMK.

After settling on a load, it averaged out at 2768 across six shots. I took the data I got from the chrono to a distance of 804 to true MV and it ended up being 2764 once that was completed.

I don't mean that when comparing two shots that the one with a higher charge will always be faster. Far from it. But on average, that is the case.

 

[Ledd Slinger]

These tests don't tell you anything except the relationship between velocity and charge weight. There is no such thing as a velocity flat spot. It's just statistical variation. More powder = more speed. In the narrow range we shoot in, the relationship is practically linear. (It's actually a curve that diminishes in slope as you increase the powder charge. There is no serious engineering literature describing a flat spot, and neither is there any known physical explanation for why one would exist. I know shooters swear by it, but it's just not true. It would be unlikely to create a chart like this and *not* see a flat spot, but don't fall into the trap of thinking it's anything but random.

I should throw in that they also give you a (poor) estimate of SD, which can be useful but generally won't be a "node" necessarily. In my experience, that does seem to correlate to powder charge somewhat, which can be explained by optimizing the combustion to get consistent results.

I think the misconception comes from a ladder test, which *is* legitimate. But that is a plot of velocity (not charge weight so you can eliminate variation) vs the vertical position of the impact. If you plot that, you will see multiple flat spots - a star step pattern (hence the title "ladder"). You want to aim for a velocity in the middle of one of those steps.

I was running a ladder a couple weeks ago and when the rifle was transitioning from a lower node to an upper node (based on POI on target) I had a big velocity spread on the transitional charge weight between the two nodes. The upper speed bullet on the spread of the transition weight was the same as others in the upper node and hit in the same spot vertically as the rest of the bullets in the upper node. the lower speed round was much closer to the speeds of the lower node and hit in line vertically with those rounds. All shot at 870 yards. The next charge weights up to max pressure stayed in the upper node impact zone.

Had I just been firing at 100 yards and just recording speeds, I would have had no clue what to expect from that speed spread in that charge weight an in no way know what was going on. But seeing the impacts on paper at long range (and talking to a friend of mine that is a very accomplished 1K BR shooter), it helped me understand what was happening. All the other charge weights in the lower and upper nodes only had an ES of less than 10 fps. So I only saw the big spread when the rifle was transitioning nodes. Total speed difference between the lower and upper node was about 60-70 fps.

Now switch to one of my different rifles in a different caliber using different bullets, powder, and primers, I’ve run ladder tests where you could stack three 3 shot groups (9 rounds) on top of each other with a charge weight spread of 1.5gr and a velocity spread of 60-80 fps. Go figure...

So as we both agree, reading speed alone doesn’t really tell us anything. Shooting paper and analyzing point of impact of bullets is the only way to know what’s going on and what the rifle likes.

 

[RegionRat]

When things like ammo tests are well behaved, the rough relationship between an SD and an ES trends to 6X as the data fills in. When you don't see that trend, you are either seeing something under sampled, or you have something that isn't behaving well, or both.

So for example, when you see Step 6 and a SD of 10 but an ES of 9 in the combined brass column, it says something needs to be looked at again. Even if it is just to discover the ES is 19... There isn't much point to calculating SD for such small samples.

The once fired samples tended to look different than the virgin samples, that was unfortunate but it happens. Unless you are truly interested in mixing those processes, then mixing the results doesn't make sense after seeing your tests. Before you go out again, I would suggest you keep those separated (just on the hunch) unless you are willing to burn up more test samples to prove to yourself they can be mixed one way or the other.

I also agree with the others that your test distance needs to be much longer and you would rather see the verticals or groups along with those velocities, rather than just the velocities. I would seek a friend with an eTarget like a ShotMarker and beg for a day at 600 yards or more. The eTarget makes collecting the groups or verticals much easier.