LRRPF52 Wrote:For a case like the Grendel with roughly 30 grains of usable powder capacity, you should consider looking at working with .3gr increments (1% of case volume) so you can get more resolution.

That 26.5gr load does look nice, but could be deceiving.

I like using pressure ladders working up in increments with 1 charge per weight in each ladder, as opposed to how I used to do it with 5 loads per weight.

I can find a good load really quick by looking at the velocity difference between nodes in the ladder, then experiment in those nodes and rule out the rest to save time and components.

Harpoon1 Wrote:LRRPF52

When you say “pressure ladder” do you mean the Satterlee method, looking for speed plateaus/nodes with a chronograph or doing a conventional “ladder” test, shooting them at distance and looking for vertical clumping?

LRRPF52 Wrote:Either/or and both, depending on what type of accuracy you're looking for.

I normally just do chronograph and call it a day once I've played with the node on a 2nd trip and get the kind of 10-shot groups I'm looking for.

Then I go shoot steel with that load and don't look back.

If someone is really chasing tight groups at distance, then it might be worth your time to do a 300yd Optimum Barrel Time work-up with scatter plots and a lab-grade scale.

The problem with .5gr increments in such a small case is that you can spike and not see the trend, then think you have a good load.

The .5gr increment habit comes from the .30-06, where you have a lot of charge weights around 50gr, so 1% of case capacity is .5gr.

Harpoon1 Wrote:LRRPF52


When you say ?pressure ladder? do you mean the Satterlee method, looking for speed plateaus/nodes with a chronograph or doing a conventional ?ladder? test, shooting them at distance and looking for vertical clumping?

Lemonaid Wrote:The cost savings really appeal to me!

Klem Wrote:My take on the Satterlee 10-shot method and a ladder test is that they are different versions of the same thing; even more so if you shoot more than 10 rounds using Satterlee. With Satterlee you are looking for plateaus in a sinusoidal velocity graph. The assumption with Satterlee is that in the powder ranges where there is less velocity dispersion will translate into tighter groups on the target.

If you are looking at results on the target this will be a version of a Ladder Test; where velocity is moot because it's tightest groups is what you are after and who cares what velocities get you that.

Using Satterlee's 10-shots to find the powder range that will give you the tightest groups (presumably the tightest groups, because you are not looking at the target, you are looking at chrono velocities) is to my mind ignorant of reality. While it is seductive to think you can find the gun/ammunition node using only 10 shots and not even look at the target you are assuming no other variables are in play and that velocity is a good predicator of group size. It could be that neck tension varies across the 10 cases, or the chronograph's inherent error confounds the findings (e.g. Chrony lists their accuracy is 99.5%, which is a sneaky way of saying they admit a 0.5% error rate. O.5% of a typical 2,400fpsMV is up to 12-fps incorrect plus or minus = it' will be somewhere within a 24fps range of the correct velocity, every shot), or if using an optical chrono the clouds give a wonky reading etc etc. Or, the velocities can be perfect but the bullets veer off course and in reality give different group sizes because the barrel behaves differently at certain velocities. Frankly I think the whole technique assumes too much. It assumes one cause is the effect, and makes no allowance for variables.

A ladder test is much closer to reality because you are not relying on velocity to tell you where the bullets should be going. You are relying on where the bullets actually go on the target.

You can use Satterlee with more than 10rds of course and when you do that you combine the methods for a more dependable outcome. The whole idea of a group is that the Mean Point of Impact is an average of a number of shots, which is because there will be variations in the factors that affect the group each time you pull the trigger. These factors include: the weather (e.g. wind), ammunition, shooter, gun and rest. It's a game of statistics and averages. 10-shots only, using a different powder charge each time is deliberately ignoring the statistical nature of shooting. It's like a snake oil salesman trying to sell you something that is too good to be true.

If you can shoot at the target at the same time you are reading the velocity that is the better option, and with a Lab Radar, or Magneto or carefully lining up your skyscreens with the target on a tripod (a pain I know, but doable), and shoot groups, not individual powder charges, then you stand a better chance of finding accuracy nodes with confidence.

I shoot one or two four-round groups for each powder increment at 100yds. Powder increments are at least 1% of total volume so variations are not swamped by lesser variables.

I would be cautious shooting further than 100 when doing basic load testing as wind becomes a factor. Wind doesn't just push bullets left and right, but also up and down (slightly - and slightly is all you need to compromise a ladder test). Truth be known, with a right-hand barrel twist wind variations string more diagonal; top left to bottom right so there's a vertical component of wind that will confound your results if you let it by shooting longer ranges. By all means once you've found a node closest to the maximum safe load then confirm at longer distances, especially if worried that after apogee on an over-stabilised bullet it might resist pointing at the target, or if approaching transonic and you want to see how big the groups blow out between various load options. These are things that shooting at 100 will never tell you.

I shoot at the target and use the Labradar to record velocity at the same time. Then combine group sizes with velocities on the same graph and look for patterns. It's never perfect but it will be even less perfect if you follow Satterlee without accounting for the statistical nature of shooting. Here's a typical result:

[ATTACH=CONFIG]15308[/ATTACH]

In this case I am expecting a sinusoidal graph of group sizes. The tightest groups should have a corresponding plateau in velocity (because variations in velocity cause variations in group sizes)

Making sense of the graph
In an overall sense it looks stable/predictable so it's likely that nothing else has influenced it more than the differences in powder charges . There is a sinusoidal group size happening but the corresponding velocity plateau is the opposite of what you would expect. In this situation I ignore velocity because rounds on the target is a closer indicator of what you want to know. If using Satterlee and not shooting at the target you would have honed in on the plateau which is the wrong result. I'm not saying Satterlee is incorrect every time, but just useless because it assumes too much and does not take into account enough variables.

Next, look for the peaks and troughs in the red line; the group sizes. Peaks are the worst groups and troughs are the best so focus on the troughs. There are two troughs in the usable powder range; 26.5-26.7gns and 27.3-27.5gns. Obviously the higher velocity is better for range and impact on target (hunting) but the group sizes are better at the lower velocity 26.5-26.7. This is a dilemma. You can either run the test again to make sure that result is repeatable or you can make a decision as to whether you want a higher veloctity with an acceptable group size, or a lower result with the best group size.

Obviously the more you shoot at each increment the more dependable the outcome. You can repeat on another shooting session to validate the earlier results. The graph lines on Excel automatically adjust each time you add more data to the range.

Moral of the story, I don't think there is one best way to load test but at least look at the target for your results. Velocities from a chronograph (only) is a clumsy proxy for actual results on the target. Plus, shoot groups instead of single shots at each increment if you can.

Klem Wrote:That's fine, but how are you going to validate what (only) 10 rounds is telling you?

Saving a few dollars when doing something as important as finding the optimum load is unusual. Like buying a car and only putting a cup of fuel in it, thinking the dollars saved (in not driving it) is thrifty.