Dumb Ladder Test Question

This is probably a dumb question, but I'm an old fart (71) and I'm allowed to ask dumb questions.
In doing a ladder test with a particular powder & bullet, how do you determine the powder increments, ie .1 gr, .2 gr, etc, that you increase with each set (5) of loads? QL goes by 2% which seems a bit much. In my case It's a 6.5x47 Lapua with a 130 gr Berger VLD with Varget.

 

I usually do .2 and then see what happens in between if it looks promising.

 

2% seems about right, then I fine tune from there

 

Varget in the 36.7 range works real well for the 140gr Bergers. ( @ 2780 ) mild load but accurate in my 6.4x47 Lapua.

 

Not a dumb question . go with .2 -.3 ,my 30" 8tw likes 38.55 gr of varget with the 130 vld @ 2962 fps . as always start lower and be safe . good luck dave

 

.5% is a good rule of thumb for ladder tests.

Well, it’s what use as a starting place.

CW

 

Rule of thumb: accuracy nodes are typically about 3% in charge apart.
The size/capacity of the case and how many nodes wanting to cover efficiently, is how I determine the increments.
For roughing in, I want lots of coverage across several nodes, there for larger increments.
For finer tuning, I only need limited coverage, there for smaller increments.
My 2-Cents

 

I usually do 0.3gr increments to make sure i don't miss an accuracy node.

And if in doubt, ask...

 

1% increments while finding the pressure ceiling.

0.2 grains when honing in on a specific load range.

 

the guy that started the ladder format said 0.2 gr steps, 20 steps one of each at 300 yards. (chrieton Audette)
if you are loading 5 of each you are not doing a ladder you are doing GROUPS. ( a ladder is designed to help you find when and where to do grpups)
typically today 1/100 of case capacity is a good step

 

I've been doing ladder tests since 1975 and my mentor suggested I do a course run at .010 grain of my load with ten cartridges. So .010X36 grains= .036 grains. It amazing how accurately this has worked out since way back then. In this rough test I look for the maximum ceiling. I take the best loads closest to max and do another ladder test with half of the .010 grain factor.

 

IMHO
this is too coarse/to large of a step for anything but a hunting rifle with no base line available.
add a zero to that step...1/100

 

That big of a jump can be dangerous, coarse steps I typically load 1% of max. For fine tuning, I will do 0.1gr steps. I cant ever imagine increasing a charge 10% at a time, some cartridge and powder combos dont even have a 10% spread from min to max.

 

That is nearly exactly how my 6BR performs. Nodes at 28.2 2690, 29.0 2770, and 30.0 2850. I found at 30.0 I can load 29.9, 30.0, 30.1 and see no change even a 500. Wish I could get to the higher node but hard bolt lift. Mike

 

You are correct. My blunder! It's .010 of the load for increments.

 

A case with 75 + gr of powder capacity, I use 0.5 gr increments.

A case with 50-60 gr capacity I use 0.4

35-45 gr capacity I do 0.3

25-35 gr capacity in 0.2

 

I look at book max velocity and deduct one grain and use that as my ceiling. I deduct 8% from the ceiling and deduct the difference between the "low" number just arrived at and that of the ceiling. Say the ceiling is 40 grains number (-) 8% = 36.8 grains. The difference is 3.2 grains a an example. Take the 3.2 grains and divide by 5 = .64 grains (.6 to round off). That will be the increase on each 5 shot group starting at 36.8 and ending at 40. I do this with several promising powders.

Then, after determining which powder looked best - I will load more of the same powder, starting one grain below the most accurate load previously fired with that powder, then increase 2/10th of a grain at a time until I am one grain above that prior accurate load. What you will be looking for is where the load is starting to shoot really well - and when it starts to decline. In a lot of medium-sized cartridges, from my experience - that might be anywhere from a 3/10 to 1 1/2 grain window where the rig shot really well. Your goal is to find that accuracy window (or "node") and know that is where you need to be. Knowing that - you might, for example, want to make your final load right in the middle of the "accuracy window" in grains. If it is freezing when you did your load development and plan on using the load during the heat of summer, you might want to make your final load at the bottom of the window, assuming a faster burn rate in summer will boost your velocity. Might do just the opposite if testing during the summer and planning on shooting in winter. Then load towards the top of the window. If you find that in final testing your window is only 3/10 or 4/10 wide, you might seek another powder that gives you the same accuracy but with a wider window. Finding one where you have 6/10 or more of a grain is ideal.

Then - I might fidget with depth adjustment a bit as a final tweak. Lots of guys do just the opposite of what I do - and that shows there are many systematic ways to narrow what you are doing. Be sure to record whether there was any wind movement and record the air temperature when doing test firings. It will come in handy if making drop charts or making loads in the future to be used in a starkly different air temperature. If your load is at the upper end of the "max" powder chart, I'd be sure to run test loads in 2/10th grain increments at least one grain higher than the load you have chosen. If your cases show any signs of excessive pressure, you will find out now where that point is- and not in the field when it gets hot. All that said - if you are loading for a .375 H&H, 1/2 to 1 grain initial loading increments are fine, whereas with a .17 hornet, 1/10th of a grain is a LOT!

 

Save yourself some bullets and powder. Load 1 round each in .3 grain intervals from starting load to max book plus 1 grain. Shoot at 300 yds. I usually start in the middle of the book loads and work up. If you start seeing pressure signs stop. Look for the nodes indicated by vertical clusters of impacts. Once you find a node then load up and shoot some groups.

 

For most of my bottle neck cartridges (250 Savage-7mm Rem Mag) i go by 0.3gr increments.
For my wifes 223 Rem, since volume is small, i go by 0.2gr increments.