Who has tried it and what are your thoughts?
http://www.65guys.com/10-round-load-development-ladder-test/
http://www.65guys.com/10-round-load-development-ladder-test/
- Thread starter bboswell
- Start date
Posting to tag. I'm about to start load development on a new rifle after Christmas. Might have to try this out.
I've been planning on trying this but since I shot my chrono this afternoon it's going to have to wait.
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IMO this method is only valid for Magneto Speed, Lab Radar or very expensive Ohler units. Your standar light based units are not accurate enough
This will work, but you should shoot three shots per charge weight. Then compare your avg velocities. One Shot is not sufficient.
I've done this using my magnetospeed chrono and was able to duplicate the results multiple times so for me it did work.
Works well for me to get a solid starting point. I start adjusting seating depth after finding the velocity flat spot. So it winds up being more a few more shots after all the tweaking. Also using magnetospeed or labradar as well.
Hopefully I will have a V3 before the end of the year. A guy a shoot with has a Labradar but it doesn't work great when shooting with a can.
I'm skeptical of this method, so I did an experiment. I did three carefully controlled "ladders" from low charge weights to higher charge weights with equal step sizes. The goal was to eliminate sources of error, and presumably the velocity flat spot should be apparent in the data if it objectively exists. The first step in error reduction was to measure the resized brass at the shoulder keeping only one length plus or minus 0.001 inches. The goal of this is to keep the initial conditions of the case volume as uniform as possible. The next step is to weigh the measured brass and only keep one weight (less than 0.1 grains ES). Next it's important to use a very carefully measured charge, so I used a milligram scale and measured each charge to the kernel. I could distinguish between long kernels and short kernels in the H4350, and I used tweezers to select the appropriate kernel to get the correct charge. I measured the MV with a magnetospeed. The ladder was run three times at a slow rate (about 1 shot every 5 minutes), and I warmed the barrel with 10 shots of factory 6.5creed ammo at a similar rate.
results:
Each ladder exhibited what could be interpreted as a velocity flat spot between 2 or 3 of the data points, but it was not consistent between the three ladders. Additionally, when I averaged the three data sets together the result was a smooth line. The velocity increased monotonically as you add more powder. I think this method looks at random variation in the data and assumes that it's significant. I don't think the velocity flat spot exists. It seems to me that this method is like interpreting tea leaves.
results:
Each ladder exhibited what could be interpreted as a velocity flat spot between 2 or 3 of the data points, but it was not consistent between the three ladders. Additionally, when I averaged the three data sets together the result was a smooth line. The velocity increased monotonically as you add more powder. I think this method looks at random variation in the data and assumes that it's significant. I don't think the velocity flat spot exists. It seems to me that this method is like interpreting tea leaves.
I've done it several times for different calibers and loads. Sometimes you find a flat spot, sometimes you don't. Sometimes the flat spot shoots great, other times not as much.
If given the option I'd prefer to load to the flat spot. But lately my approach has been to shoot OCW style three shot groups, then look at all factors before making a decision. POI, group size, average velocity curve for flat spot, SD/ES. etc.
If given the option I'd prefer to load to the flat spot. But lately my approach has been to shoot OCW style three shot groups, then look at all factors before making a decision. POI, group size, average velocity curve for flat spot, SD/ES. etc.
I have been doing a variation of this for the past two-three years and it has worked for a 6.5 grendel, 6.5x47L and 6.5 creedmoor. The difference is I will use two or three rounds of each powder charge and track not only velocity increase/flat spots but also ES/SD of each load. The node may not have the tightest ES/SD of those tested but it generally is very close and you can see the wave so to speak in that es/sd will tighten and the widen with in the loads tested. It also seems to follow OCW predictions of each node being around 3% from each other.
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