Target free ladder test?

[Dave Way]

So recently I received a new 6BR Improved from Alex Wheeler. After forming brass, and some 500 yard testing, I decided to do a powder ladder at 1K. I tested five loads at .1 gr. increments from 30.4 to 30.8 grains of H4895 with a 103 Vapor Trail.

30.4 gr. 2,933 fps avg. ES=6 fps
30.5 gr. 2,945 fps avg. ES=8 fps
30.6 gr. 2,947 fps avg. ES=6 fps
30.7 gr. 2,953 fps avg. ES=12 fps
30.8 gr. 2,972 fps avg. ES=5 fps

The target below only includes two shots as I had planned on doing a three shot ladder but ran into an issue. For that reason, this paper ladder is based on two shots but all three shots for each charge were chronographed with my Oehler 35P to get the averages and ES's.

If you look at the velocity data and relative elevations on the target it is easy to see the "flat spot" at 30.5 to 30.6 with 30.4 printing lower and 30.7 printing higher. 30.8 appears to be getting into a load range showing vertical. 30.54 gr. has proven to be extremely accurate.

My question is this, do you think a powder node could be determined simply using chronograph data without a target? I plan on doing a similar test with another barrel I am breaking in right now to see if I get similar data.

Curious to hear your thoughts on this.

Dave.

 

[22DASHER]

You got lucky and things lined up. That’s the best case scenario. Don’t expect that every time. I would always rely on what the target tells you!

 

[MihiT]

Yep. There's no replacement for hole-placement.
In saying that, nodes picked on my ladders usually line up with a *thing* in the velocities, whether that's a peak, or a narrowing of spread between charges, it's pretty obvious reading through the list. Still, I wouldn't just take that data as gospel.

 

[JFrank]

I’d like to see you follow through with the test.
I know some PRS guys that only look at data.
They shoot out to 1200 yard with a good level of accuracy

 

[Joe Salt]

Do a 5 shot group at 1000 using 30.5 see what it does!

Joe Salt

 

[David Christian]

Dave,

I test on a very regular interval and graph my chrono data and I can tell you that my data always lines up with the target. Finding the node is very easy (see attached spreadsheet), yet fine tuning within the node for a specific distance that you plan to shoot, does take the paper to confirm. In my example I did this testing at 100 yards, then took the .4 grain node (50.6 - 50.9) out to 1,000 yards and found that 50.7 had the least vertical.

So recently I received a new 6BR Improved from Alex Wheeler. After forming brass, and some 500 yard testing, I decided to do a powder ladder at 1K. I tested five loads at .1 gr. increments from 30.4 to 30.8 grains of H4895 with a 103 Vapor Trail.

30.4 gr. 2,933 fps avg. ES=6 fps
30.5 gr. 2,945 fps avg. ES=8 fps
30.6 gr. 2,947 fps avg. ES=6 fps
30.7 gr. 2,953 fps avg. ES=12 fps
30.8 gr. 2,972 fps avg. ES=5 fps

The target below only includes two shots as I had planned on doing a three shot ladder but ran into an issue. For that reason, this paper ladder is based on two shots but all three shots for each charge were chronographed with my Oehler 35P to get the averages and ES's.

If you look at the velocity data and relative elevations on the target it is easy to see the "flat spot" at 30.5 to 30.6 with 30.4 printing lower and 30.7 printing higher. 30.8 appears to be getting into a load range showing vertical. 30.54 gr. has proven to be extremely accurate.

My question is this, do you think a powder node could be determined simply using chronograph data without a target? I plan on doing a similar test with another barrel I am breaking in right now to see if I get similar data.

Curious to hear your thoughts on this.

Dave.

View attachment 1107072

 

[Dave Way]

Do a 5 shot group at 1000 using 30.5 see what it does!

Joe Salt

How about 10 shot?

 

[DHuffman]

That should work LOL!

 

[Dave Way]

The reason for my post wasn’t because I questioned the node I found. I have tested it and am happy. It was to see if others had been able to correlate strictly velocity data with an accuracy node. So often, it seems the wind doesn’t want to cooperate when I want to shoot a ladder, particularly a 1,000 yard ladder.

It sure would be nice to fire your test over a chronograph and not have to worry about conditions while fully understanding eventual paper testing at distance would be required to verify the load. Maybe even just use the velocity data to narrow down the window for the paper ladder testing at distance with a cartridge that was new to you.

Beyond all of this, the question is still “Why do velocities flatten out even while increasing powder charge”? I have heard various theories on that.

Dave.

 

[ballistic64]

I’m trying the method with a new 6.5x47. Found a velocity flat spot with 39.8-40.4 with H4350 and a higher velocity flat spot with 38-38.4 of RL15.
I took the H4350 up to 42 gr, but didn’t find another flat spot even close to the 39.8-40.4 gr loadings. It is going to have to dry out quite a bit before I get a chance to do the ladder with these loads. Snow at the end of May, it’s going to be a short summer.

 

[Joe Salt]

Dave I believe your at the node you want to be at, but you were wondering about velocity flat spot. If you were to keep going with powder I think you would get a spike it velocity and that is were you don't want to be. Your two shots in the eight ring were probably conditions. Have you tweaked the seating depth at all.

Joe Salt

 

[Dave Way]

Dave I believe your at the node you want to be at, but you were wondering about velocity flat spot. If you were to keep going with powder I think you would get a spike it velocity and that is were you don't want to be. Your two shots in the eight ring were probably conditions. Have you tweaked the seating depth at all.

Joe Salt

Joe,

I hope to see you at a Williamsport match before the World Open. I have tested seating depth and am currently .004” in. I’m going to test meplat trimming without pointing and see it it helps with that last bit of vertical.

Thanks-Dave.

 

[CharlieNC]

Don't forget you are also dealing with barrel harmonics. While a chrono node is nice, it does not assure the barrel vibration is at an optimum point in its cycle to provide compensation to minimise the effect of velocity variability. The target alone reflects the combination of these two factors.

 

[Joe Salt]

Dave if you're going to be at the next match look me up! I don't remember ever having barrels that ever worked for me that had the bullets in the lands. Right know I'm working on some 215 hybids started off touching but had a little vertical. Shot a 7.6- 94 so I'm backing them up 5 thou. to see if that helps. Any time I fine a node I play with seating depth. Remember if you start in there is only one way to go!
Charlie your right on the harmonics that's why I just change one thing at a time.

Joe Salt

 

[Dave Way]

Dave if you're going to be at the next match look me up! I don't remember ever having barrels that ever worked for me that had the bullets in the lands. Right know I'm working on some 215 hybids started off touching but had a little vertical. Shot a 7.6- 94 so I'm backing them up 5 thou. to see if that helps. Any time I fine a node I play with seating depth. Remember if you start in there is only one way to go!
Charlie your right on the harmonics that's why I just change one thing at a time.

Joe Salt

Joe,

This barrel definitely likes them in. Not the best photo but the only difference is .004” in on the left and .005” out on the right. Same load. Shot at 1K in good conditions. 2.3” to around 10” or so, all vertical.



Dave.

 

[Joe Salt]

All I can say is keep them in!

Joe Salt

 

[Webster]

There is no such thing as flat spots related to accuracy. The term is bogus it assumes close to zero ES. The line is a best linear fit thru all the data points. Most guys use .3 gram increments. I used the OP's charge and fps to creat this chart. If you let Excel's statisticals add error bar's for fps spread it shows there is nothing that resembles a flat spot. Statistics estimate a 15 ES for many shots at each load.
Having trouble clipping and pasting. I hope it looks OK?

R2 is an estimate of accuracy. Above .96 is pretty good. More shots would raise the R2 and the average for many shots would be much closer to the best fit line.

 

[David Christian]

View attachment 1107618

There is no such thing as flat spots related to accuracy. The term is bogus it assumes close to zero ES. The line is a best linear fit thru all the data points. Most guys use .3 gram increments. I used the OP's charge and fps to creat this chart. If you let Excel's statisticals add error bar's for fps spread it shows there is nothing that resembles a flat spot. Statistics estimate a 15 ES for many shots at each load.
Having trouble clipping and pasting. I hope it looks OK?

R2 is an estimate of accuracy. Above .96 is pretty good. More shots would raise the R2 and the average for many shots would be much closer to the best fit line.

@Webster can you explain this further? I have found flat spots related to charge weights in each and every test that I have done. Can you please describe your load development technique using R2? Thx DC

 

[Webster]

@Webster can you explain this further? I have found flat spots related to charge weights in each and every test that I have done. Can you please describe your load development technique using R2? Thx DC

I don't shoot in competition. I don't use R2 to develope loads. I shoot at targets. If you plotted the average fps for a large number of shots at each load the you should be able to draw a straight line thru the data points, no flat spot. More powder more fps with an ES spread. Charts with flat spots only exist because you are plotting a small number of shots at each load and it ignores the fact that the ES for 10 shots would be bigger and more accurate and the average fps would be more accurate. One shot at a load may be at the high end of the ES, you increase the powder and the next shot is at the low end of the ES. They are not flat because something unique is happening that allows no or little increase in fps with a powder increase. To sum everything up ignore flat spots and determine accuracy by looking at targets. There are no short cuts. Tony Boyer is the best short range BR shooter that ever lived he developes and tunes his loads by his targets. He has about 100 Hall of Fame points more than his nearest competitor. I only put the charts up to prove there is no real flat spot.

 

[CharlieNC]

I don't shoot in competition. I don't use R2 to develope loads. I shoot at targets. If you plotted the average fps for a large number of shots at each load the you should be able to draw a straight line thru the data points, no flat spot. More powder more fps with an ES spread. Charts with flat spots only exist because you are plotting a small number of shots at each load and it ignores the fact that the ES for 10 shots would be bigger and more accurate and the average fps would be more accurate. One shot at a load may be at the high end of the ES, you increase the powder and the next shot is at the low end of the ES. They are not flat because something unique is happening that allows no or little increase in fps with a powder increase. To sum everything up ignore flat spots and determine accuracy by looking at targets. There are no short cuts. Tony Boyer is the best short range BR shooter that ever lived he developes and tunes his loads by his targets. He has about 100 Hall of Fame points more than his nearest competitor. I only put the charts up to prove there is no real flat spot.

While it may be possible to identify a velocity flat spot, the number of reported observations used are always too few as you suggest. And it will require more to achieve suitable average velocity results ( like n=10) than relying on the target where 1 or 2 shots per charge for a ladder are suitable. Amazingly a few years ago the loading world was set on fire by the guy espousing 1 shot per charge to find the chrono flat spot, amazing illogical nonsense.