Ladder Test Increments & Range with Chrono

[rookyshot]

I'm about to start developing a load for my 243 with Sierra Pro Hunter 100gr bullets and Reloader 19 powder in Lapua case.
In my load development to date with my 223 I've loader 5x rounds for each powder increments and test shot groups to see which increment has given me the tightest groups in a traditional reloading approach.

I now have access to a Chronograph and would like to have a go at ladder testing on the Chrono to try and identify the charge weight which offers the lowest ES / SD to see if that correlates with the tightest groups. Looking at Sierra's load data for my bullet and powder combination it provides a charge weight of 38.3gr - 42.2gr which is a range of 3.9gr

What I'd really appreciate some guidance on what increment in charge weight I should be testing and if I should be testing the whole charge weight range from 38.3 - 42.2 to identify accuracy nodes. For example if I was to test the full range at 0.2gr increments the ladder will be 20 rounds but from what I've read it appears that a lot of people are conducting 10 round ladder tests.

Any guidance on the best approach would be really appreciated as one of the reason's I purchased a Chrono is to reduce the number of test rounds that I need to load in my initial stages of load development on a round.

Many Thanks RookyShot

 

[Bavarianbrit]

I have just found this Hodgdon data calculator which may help.
You type in the Hodgdon/WinchesterIMR powder choice and voila Robert is related to you.

Reloading Data Center

www.hodgdonreloading.com

 

[Coddy]

 

[Rusty Gate]

Id go up in 0.3`s.
Think youd start & finish on the same figures olus it shoukd give you a nice plot if you do the graph to see the nodes

 

[Steff]

One of the characteristics of a good load is that it is tolerant to minor variations. Therefore I see no sense in going in 0.2 or 0.3 grs. increments. I go in 0.5 or 0.6 grs. increments. Once you have found something within this rough grouping you can still do some fine tuning.

 

[Selous]

I use single shots at 0.3 grain increments as a rule and look for uniformity of velocity across 2 increments. If I were to use 0.2 gr increments then I would look for three adjacent increments giving similar velocities. Once I have identified likely nodes I then load 3 rounds at 0.1 or 0.2 grain increments around the suspect node and shoot for group and uniformity of velocity

 

[Sonicdmb73]

I have a slightly different approach. It makes your steps consistent regardless of cartridge you’re loading for.
Go up from minimum (usually 10% below max) in 1% increments. I round the results to the nearest .1 grain which is what my scales read.
So your start weight of 38.3 + 1% = 38.683 rounded to 38.7. Do + 1% again you get 39.06983 so round to 39.1 grains.
You get even steps proportional to the case capacity. Regardless of case size, which you don’t with the traditional .5gn or .2gn that many use. Don’t get me wrong that works. But if you are looking for an even spread across the weight range. Then percentage is the way I have found.
I put in the minimum load and then just keep adding 1% and writing the result down, then round those afterwards.

 

[Totsy]

I have a slightly different approach. It makes your steps consistent regardless of cartridge you’re loading for.
Go up from minimum (usually 10% below max) in 1% increments. I round the results to the nearest .1 grain which is what my scales read.
So your start weight of 38.3 + 1% = 38.683 rounded to 38.7. Do + 1% again you get 39.06983 so round to 39.1 grains.
You get even steps proportional to the case capacity. Regardless of case size, which you don’t with the traditional .5gn or .2gn that many use. Don’t get me wrong that works. But if you are looking for an even spread across the weight range. Then percentage is the way I have found.
I put in the minimum load and then just keep adding 1% and writing the result down, then round those afterwards.

This is what I do with the exception that the first two loads starting 10% below max go up in 2% increments as they are just checking the powder/bullet combo is safe. For the OPs .243 powder weights the 1% increase will round up to 0.4gn Steps from experience.

 

[1894]

Factor in the accuracy of our scales. If it’s +/- 0.1grains it’s pretty pointless doing 0.2gr steps IMHO.

 

[jcampbellsmith]

I'm about to start developing a load for my 243 with Sierra Pro Hunter 100gr bullets and Reloader 19 powder in Lapua case.
In my load development to date with my 223 I've loader 5x rounds for each powder increments and test shot groups to see which increment has given me the tightest groups in a traditional reloading approach.

I now have access to a Chronograph and would like to have a go at ladder testing on the Chrono to try and identify the charge weight which offers the lowest ES / SD to see if that correlates with the tightest groups. Looking at Sierra's load data for my bullet and powder combination it provides a charge weight of 38.3gr - 42.2gr which is a range of 3.9gr

What I'd really appreciate some guidance on what increment in charge weight I should be testing and if I should be testing the whole charge weight range from 38.3 - 42.2 to identify accuracy nodes. For example if I was to test the full range at 0.2gr increments the ladder will be 20 rounds but from what I've read it appears that a lot of people are conducting 10 round ladder tests.

Any guidance on the best approach would be really appreciated as one of the reason's I purchased a Chrono is to reduce the number of test rounds that I need to load in my initial stages of load development on a round.

Many Thanks RookyShot

It depends is the short answer. If you've never used the powder/bullet combination before, then be cautious. In recent times I've shot velocity tests with increments of 0.1, 0.15 and 0.2 grains.
Regards
JCS

 

[Sonicdmb73]

This is what I do with the exception that the first two loads starting 10% below max go up in 2% increments as they are just checking the powder/bullet combo is safe. For the OPs .243 powder weights the 1% increase will round up to 0.4gn Steps from experience.

I admit I don’t religiously start at minimum (10% under) anymore. However I have loaded a lot of rounds for my rifles and know what I should get both speed and accuracy wise. So can skip a few steps, as long as the chrono and cases are ok.

Factor in the accuracy of our scales. If it’s +/- 0.1grains it’s pretty pointless doing 0.2gr steps IMHO.

I suppose it depends on what scales you use. Mine will tell you the difference down to one or two kernels of powder. The only thing I want to add is a camera and screen so I can eliminate parallax and unless you get lab scales I doubt you will improve on the accuracy.

 

[rookyshot]

Thanks for all the replies and PMs on this subject, really useful and I'm looking forward to getting going on my load development over the Easter break..

 

[crow juice]

I am doing a similar test right now with my 6.5 Creedmoor at 0.5 grain increments . I am using N203b , Speer 120 gr Gold Dots , Hornaday cases , and Federal 210 Primers . I am using a Ohaus 5-0-5 scale verified with check weights and a Lee Deluxe powder measure.

I am using thrown charges with measured variations of plus or minus .1 grain with the N203b. I am planning on using thrown charges so right or wrong that is how I am testing.

 

[Sonicdmb73]

I am doing a similar test right now with my 6.5 Creedmoor at 0.5 grain increments . I am using N203b , Speer 120 gr Gold Dots , Hornaday cases , and Federal 210 Primers . I am using a Ohaus 5-0-5 scale verified with check weights and a Lee Deluxe powder measure.

I am using thrown charges with measured variations of plus or minus .1 grain with the N203b. I am planning on using thrown charges so right or wrong that is how I am testing.

I used to load some very accurate ammunition. Using the Lee powder measure, less than 1/2 MOA in my 243.
Plenty enough for minute of fox as far as I ever wanted to take a shot.

 

[aquarius11]

Just did my load development went up in .5grains, two things I realised I need.
1 better scales
2 position the chrono better to read every shot.
I'm loading 39.5gr now as this group was 7/8" at 200yds but the velocity varied 273 FTPs over 3 shots.
Next is seating depth.