Load Testing, Chrono, Accuracy, How do you proceed.

[TattooedGun]

So, historically, I've loaded 4-5 rounds of each powder load and shot each 4-5 rounds at a 1" target some 100 yards away.

Not having a Chrono I used Quickloads best efforts to find speed and have been fairly successful with this method.

I'm just about to embark on 2 lots of new components that i want to load for my .308.

Add into the mix that I have also acquired a Magnetospeed V3...

Now, I don't want to shoot for accuracy with the bayonet fitting chrono on, so I'm thinking making an additional 3 rounds per load up so I can Chrono each load to see where I'm at on one visit. I can then use the Chrono Data, small though it is, along with the target data to let me know my best load.

Is there perhaps a better way I could conduct this test?

I'm not worried about using lots of components and bullets or whatever, This will be the first time I've been out with this rifle this year due to other commitments, so I'm excited to shoot as much as possible, But I want to end up with the best possible combination given my time.

Components:

RWS Once Fired, FL Sized Cases
CCI 200 primers
N140 Powder

155gr Amax / Dyer HBC 155gr

Current accuracy node for amax and N140 I'm using is at 46.4gr, though I'm welcome to trying a lower node.

Would the following batches be a good starting point...

bowl Amax @ 42gr N140 / bowl HBC @ 42gr N140
bowl Amax @ 42.5gr N140 / bowl HBC @ 42.5gr N140
bowl Amax @ 43gr N140 / bowl HBC @ 43gr N140
bowl Amax @ 43.5gr N140 / bowl HBC @ 43.5gr N140
bowl Amax @ 44gr N140 / bowl HBC @ 44gr N140
bowl Amax @ 44.5gr N140 / bowl HBC @ 44.5gr N140
bowl Amax @ 45gr N140 / bowl HBC @ 45gr N140
bowl Amax @ 45.5gr N140 / bowl HBC @ 45.5gr N140
bowl Amax @ 46gr N140 / bowl HBC @ 46gr N140
(I already have some Amax @ N140 46.4gr made up) / bowl HBC @ 46.4gr N140

Then an additional 3 rounds of each load for a 3 round average over the chrono...

I've read a little about ladder testing, would it be worth shooting 4 shot groups and using 1 round from each to do a ladder test with these rounds? Would that give me more useful data about where the harmonic loads may be, so there's less elevation change should the powder charge vary by a few .1gr...?

Always looking to improve my procedures, and I'd like to do a writeup on this procedure, so any tips on how to better my load testing procedures would be hugely appreciated.

Cheers

TG

[JSC]

If you're using QL there's a method I use which saves time and components.

Using your example loads, first load 2 of each with your incremental charges of N140 from 42-46gr in 0.2 or 0.3 increments, depending on how accurate you want to go.

Then shoot these over the chrono so you obtain a reasonably accurate graph of powder charge vs. MV. Two of each gives you some backup in case of strange readings. Or you can average each of the pair and use that as your MV.

Now plug the powder charges and all your other load data into QL and adjust the variable Ba (burn rate) for B140 until the MV matches or gets close across the range of charges you tested.

This will allow you to see which nodes you can get to and give you a pretty accurate load for each node.

Let's say QL is telling you 44.0 is at the right MV to hit a node.
Now load another batch of test rounds, 5 rounds of each charge from 43.7-44.3 using 0.1gr increments. Shoot 5 round groups with these at 300yds at least, preferably 500 or 600yds.

You could do a ladder test as well to confirm this method has produced the optimal charge weight.

I find ladder tests can be inconclusive and you need to do them at 300 yds minimum to really see what's going on, which can make it difficult to do without a marker in the butts. My method above is something you can do on your own if you wish.

[TattooedGun]

If you're using QL there's a method I use which saves time and components.

Using your example loads, first load 2 of each with your incremental charges of N140 from 42-46gr in 0.2 or 0.3 increments, depending on how accurate you want to go.

Then shoot these over the chrono so you obtain a reasonably accurate graph of powder charge vs. MV. Two of each gives you some backup in case of strange readings. Or you can average each of the pair and use that as your MV.

Now plug the powder charges and all your other load data into QL and adjust the variable Ba (burn rate) for B140 until the MV matches or gets close across the range of charges you tested.

This will allow you to see which nodes you can get to and give you a pretty accurate load for each node.

Let's say QL is telling you 44.0 is at the right MV to hit a node.
Now load another batch of test rounds, 5 rounds of each charge from 43.7-44.3 using 0.1gr increments. Shoot 5 round groups with these at 300yds at least, preferably 500 or 600yds.

You could do a ladder test as well to confirm this method has produced the optimal charge weight.

I find ladder tests can be inconclusive and you need to do them at 300 yds minimum to really see what's going on, which can make it difficult to do without a marker in the butts. My method above is something you can do on your own if you wish.

Thanks for the info.

Unfortunately, shooting out to 300 yards is difficult as finidng range time is hard at the moment. I will be doing most of my testing at 100 yards since theres a range I can get to to go shoot (Minsterley). I wish I lived closer to Bisley and I'd become a member there to do some decent load testing.

How do you find where QL would be at a "node"?

[JSC]

OK, so I'd forget ladder tests as at 100yds it's going to be difficult to see much of a difference between each shot. Stick to group testing but at least 5 round groups. Most people shoot 3 round groups to save ammo, but if this isn't a concern 5 rnd groups will be much more revealing.

To find out where the nodes are, use an OBT table like this one:http://www.the-long-family.com/OBT%20Table.pdf
That website is worth looking at if you are new to the OBT concept and it will give you more tips about how to use it with QL.

In the results window in QL, there is the Barrel Time variable measured in ms, which is the number you are looking to match against the OBT table values.

[WelshShooter]

A node is defined as a charge weight which when altered a small amount has no significant effect on the velocity. An X by Y scatterplot of charge weight vs muzzle velocity would produce a positive correlation. However, it's not going to be a straight line. There will be points where it will flatten out slightly, before continuing to rise. These flat regions indicate that a small change in charge weight produces no nett change in velocity, or at least not a significant one.

Use the nodes as a good starting point, make up a small batch of maybe n=25 and shoot some groups to see how repeatable they are. Assuming that you do your part behind the rifle, look at your WORST groups, not your BEST. A load which shoots 0.5moa consistently is better than a load which shoots between 0.2moa and 0.8moa depending on whether the planets are aligned etc. This is where a larger sample size will be of benefit - is your load repeatable?

Some people may opt to change the seating depth at this point, but I generally do this at the earliest stage in load development. Some bullets like a bit of jump, others like to be seated just off the lands. Do a bit of research on your bullet type and see what other people have had luck with.