First time with handloads trying to decipher chrono data.

[Schroedernd]

First time doing some hand loads and looking for some assistance in reading my groups. This is for 69gr SMK HPBT over Reloader 15 in my Savage FCP-k 1:9 with a 24" barrel in a XLR Chassis 20k of the lands (I called the one flyer on the 25.2). My thought is to do some 25.2, 25.3, 25.4, 10k of the lands, yet technically the 25.6 had the best SD and ES but crappiest group. Any other thoughts? I plan to use this to shoot to 800y on calm days to give a break to my creed and grendel. I did not do the ocw method and am trying the 6.5 guys method http://www.65guys.com/load-development-part-1-of-2/

 

[Schroedernd]

[No message]

 

[pell1203]

I think 25.2 to 25.3 will be your sweet spot. Fairly tight groups in the same location with very similar velocities. The 2983 fps at 25.4 seems to be a bit of an outlier.

 

[Sheldon N]

Agree, I'd probably load right at 25.3. If you put your velocities to a line chart you can easily see the flat spot in the velocity curve.

 

[Schroedernd]

That was kind of my thought. I think I will load up some 25.2, 25.3, and 25.4 10 thousands of the lands and see what the chrono says. Hopefully i get a load out of one of them. I was thinking that slow one in the 25.4 and fast one in 25.2 were a loading mistake or else that 25.2 would've had single digit SD.

 

[Schroedernd]

Agree, I'd probably load right at 25.3. If you put your velocities to a line chart you can easily see the flat spot in the velocity curve.

I wanted to do a chart like that but had no idea where to start. On a plus note, i got the equations for SD and ES figured into an Excel spreadsheet that made it easy to get my numbers since I am using an old chrono that doesn't log. Thanks for the chart!

 

[Sheldon N]

It's pretty easy to make the chart in Excel, put charge weight in one column and average velocity in the second column next to it. Highlight both columns then go -> insert -> scatter -> scatter with smooth lines. Boom, you're done.

I started using the excel graph method this last time around with load development. I tried it a little differently, shot two rounds at each charge weight with the magnetospeed attached to get velocity data. Then shot the remaining 3 rounds with the magnetospeed off at each charge weight as an OCW style test. Sure enough, the OCW showed a POI node exactly at the same place where the flat spot in the velocity curve was, and that was the smallest group, and it has single digit SD's.

I think on future load development I'm going to to straight to the chrono first, shoot a broad set of charge weights with just 2 rounds each to get a big picture velocity curve, then shoot OCW style tests only in the area the velocity curve is flat. Will probably take less rounds and focus my efforts on the areas with the most promise. Would be even better if I had a labradar.

 

[Schroedernd]

It's pretty easy to make the chart in Excel, put charge weight in one column and average velocity in the second column next to it. Highlight both columns then go -> insert -> scatter -> scatter with smooth lines. Boom, you're done.

I started using the excel graph method this last time around with load development. I tried it a little differently, shot two rounds at each charge weight with the magnetospeed attached to get velocity data. Then shot the remaining 3 rounds with the magnetospeed off at each charge weight as an OCW style test. Sure enough, the OCW showed a POI node exactly at the same place where the flat spot in the velocity curve was, and that was the smallest group, and it has single digit SD's.

I think on future load development I'm going to to straight to the chrono first, shoot a broad set of charge weights with just 2 rounds each to get a big picture velocity curve, then shoot OCW style tests only in the area the velocity curve is flat. Will probably take less rounds and focus my efforts on the areas with the most promise. Would be even better if I had a labradar.

Thanks for the info on the chart, I'm going to try it out. Also, take a look at this article about shooting OCW style. They recommend not using it and it seems to make sense for long range shooting. http://www.65guys.com/load-development-part-1-of-2/

 

[Sheldon N]

Yes, that's a great article and I'm taking a lot of what I'm doing from that. Ed, Steve and Scott are all good guys and I shoot matches with them up here in the NW.

I should clarify that when I shot my "OCW" test I shot 3 shot groups in sequence, not round robin. I then interpreted them based on POI in conjunction with the graph data as well as just simply looking at how well they performed in terms of group size. There have been some situations in the past where I found a load that had great SD but it didn't group very well. For long range I want everything to align... tight group, low SD, POI and velocity plateau, etc. This last go around there was another upper node that I chose not to pursue because it simply didn't group very well even though it had good SD and a velocity plateau. Sometimes you can tighten group size with seating depth but with this particular bullet I'm constrained to mag length so I couldn't do that. The low node shot bugholes so that made the choice easy too.

 

[jsthntn247]

Do a seating depth test a 25.3

 

[goldeneagle]

Thanks for that chart hint...I've used Excel for years but never for load development.

 

[Sendit6.5]

That was kind of my thought. I think I will load up some 25.2, 25.3, and 25.4 10 thousands of the lands and see what the chrono says. Hopefully i get a load out of one of them. I was thinking that slow one in the 25.4 and fast one in 25.2 were a loading mistake or else that 25.2 would've had single digit SD.

I would not recommend doing this. Change ONE thing at a time, not 2 - it's a great rule of thumb that leads to less head scratching, IMO. You clearly have a node around 25.3gr. When I have 2 good groups like you had at 25.2 & 25.3 I've had great success settling into the slot between the 2. Work with seating depth now. I would start by seating longer and longer (if you have room to do so) because I usually have better luck with less jump.


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