Ladder vs. OCW

 

Ladder vs OCW

 

Below I have listed the pros and cons of  three different load development methods:

Ladder Test, OCW Test, Classic Test

Further down the post you can read about each method in depth (including how to read an OCW Test)

 

LADDER METHOD (ADVANCED)

“It is not one reloading component which is responsible for an accurate load, but the sum of everything working together.”

Creighton Audette

Ladder Pros:

Best uses: 600-1000 yd bench rest, highly accurate/ custom rifles.

  • Precision Shooting Reloading Guide
  • Setup: Minimum of 300 yds (you can perform this test at 100yds if it is a 1 MOA rifle, sub moa/match rifles are more difficult to read because the bullet impacts can just stack on top of each other)
  • Uses a chronograph to chart velocities (extreme spreads and standard deviation)
  • 20 rounds typically used to find stable pressure (velocity)
  • Usually shot round robin (alternating sequence)
  • Minimal shots required
  • Lots of good information comes out of this test
  • Find accuracy node quickly
  • Takes wind out of the equation (horizontal stringing of shots)

Ladder Cons:

  • Hard to read the results
  • Susceptible to variables
  • Uses a lot of components (you typically perform 3 strings of each load, redo/ fine tune it more times)
  • Bad shooting technique ruins the entire thing
  • Might require more than one range trip
  • Does not consider horizontal stringing (you are only looking for the smallest group vertically. This can sometimes be misleading in reading the results of the test)

Ladder Test Tips:

  • Refer to this website for a well written article on the Ladder Test www.6mmbr.com/laddertest.html
  • USE Colored marker to identify bullets (so you don’t have to physically log each shot separately/ or use a camera at 500 yds)

Dan Newberry- Optimal Charge Weight Method (Intermediate/ Advanced)

OCW Pros:

Best uses: Can be used with a wide range of rifles and shooter abilities. Capable of great 1000 yd groups

  • You don’t need a chronograph
  • Shot round Robin (alternating sequence)
  • Warehouse project- “load shoots reliably at 100yds- it will be the same at longer range”, precisionrifleblog.com look under the MYTHS BUSTED section
  • Straightforward approach
  • Looks for point of impact shift.
  • Can be shot at 100yds
  • Easier to understand than the ladder test
  • More forgiving because it utilizes multiple shots per load

OCW Cons:

  • Uses more components to get the job done
  • Can often lead people in the wrong direction especially with vertical stringing
  • Sub moa/ match barrels will produce tiny patterns. This can make the test more difficult to read. It is still doable.

OCW Tips:

  • Use 4-5 bullets per charge weight. This helps eliminate shooter error.
  • Use a chronograph- we are looking for the powder charge weight with the highest STABLE velocity (standard deviation SD and extreme spread ES)
  • Understand the OCW terms (scatter group, ocw, accuracy node, transition group, Point of impact shift). This will help you read AND understand the OCW test. Read about these terms below in the full description of the tests.
  • Shoot the test ROUND ROBIN. low to high- then in reverse order, then low to high. This evens out the fouling in the barrel during the test.

OCW is generally 1-2% higher powder charge than the scatter node

BOTH TESTS SHARE:

  • Both have scatter and accuracy nodes
  • Both are velocity/ pressure stable
  • Resistant to temperature change
  • Both OCW and Ladder Test developed by shooters
  • Both look for a wide margin of stability (accuracy node)
  • Both shot round robin style
  • Both start with stability, and then move into precision

Classic Reloading Method (Beginner/ intermediate)

Classic Reloading

Best uses; Finding a basic accurate load, Hunting

Load 3 shells each with 1gr. increments. Find an accurate load, fine tune it, go up or down .5g to see if that tightens it up. “Seems to work for me, and I shoot no more than 20 shells altogether. Lot less confusing”. You can increase accuracy by going in .5 gr initial increments and smaller secondary increments such as .2 gr. This will avoid skipping over the accuracy node.

My father in law has used this method for almost thirty years. He is a hunter and has shot elk at 500-700 yards. He has also shot dime sized groups at 300yds with a factory rifle. This testing method does have merit

Pros:

  • You don’t need a chronograph
  • Very straight forward
  • Easiest of the three testing methods

Cons:

  • You can miss the accuracy node on the pressure curve by skipping over it by using too large powder change increment in the test
  • Need to fire the Final load in extreme temperature changes to ensure you are in the middle of a accuracy load. (20 degrees/ 100 degrees. OR just use a HODGDON H- series powder that is temperature stable)
  • Takes additional range trips/ components

Ladder Test In Depth

ES & SD @ 1000yds

“…it is much better to shoot 2,500fps ammunition with a Standard Deviation (SD) of 8 and an Extreme Spread (ES) of 20 than 2,600fps ammunition with a standard deviation of 12 and an extreme spread of 35.” (Removing INCONSISTENT results)

Creighton Audette’s Ladder Test Method

Objective: Finding the most stable operating velocity with the same POI (Precision Shooting Reloading Guide), Reduce Vertical dispersion

 

Used to Find: Optimal Powder Charge Weight, bullet seating depth, Primer Brand

Highpower 1000 yd shooter- Audette was concerned with VERTICAL shot dispersion, not horizontal (taking wind out of the equation)

“It is not one reloading component which is responsible for an accurate load, but the sum of everything working together.”

This includes; barrel harmonics (the vibration pattern of the barrel), bullet, case, powder, primer etc.. Staying away from maximum loads- He was trying to remove inconsistent performance from a load. Maximum loads can exhibit erratic behavior.

LADDER TEST

DRIVEN BY VELOCITY- WHICH CAN BE AFFECTED BY CASE CAPACITY (BRASS WEIGHT)

Uniform weight, primer pockets, flash holes deburred etc.

Then pick the most consistent part of the node for your load.

Shots/ Strings Needed

3 rounds is MINIMUM to get accurate velocity, ES, and AV data.

Three shot groups are adequate for getting mean velocities to run ballistic drop program.

One shot “groups” are not meaningful (unless you are using an OEHLER 35P or similar HIGH grade chronograph to measure velocity)

 

Accuracy Node

This is the area where the fired shots group tightly together. You are looking at VERTICAL Separation only (NOT HORIZONTAL which is due to wind). You might have to graph the results to see the accuracy node -if it is close to the scatter node.

 

The Scatter Node- May confuse the reader because the point of impact should be higher as the powder charge is increased. Instead, you will see an area of inconsistency where the impacts are all over the target. This quality is what confuses many reading the Ladder Test.

 

LADDER TEST TIPS:

  1. USE a chronograph
  1. Color your bullets with colored sharpie so you do not have to have a camera on the target. This works well for 300 + yds
  1. Shoot round robin- Low to high, then high to low, then low to high. This will naturally average the results from the barrel heating up
  1. Use a LARGE target. If it is windy you won’t have to redo part of the test from your bullets going off target due to wind or shooting above /below the target (I did my ladder test at 500 yards)
  1. By using brass that is very uniform, you are eliminating one of the variables. Your velocity spread should be smaller and the nodes easier to see.

3. An accurate chrono is absolutely essential. Any technique (ladder or OCW) w/o a chrono you can easily miss the MV jumps and nodes. (that truly is my biggest issue with OCW) That chrono information will help you confirm any suspected tuning node. Dan and I both agree that if you get on one edge of a node, it is easy to come out of tune with temp changes. The chrono will literally show the up and down edges normally. I always start my powder fine tuning in the middle of the node and rarley deviate more than .1 gr up or down, and then go with seating depth

 

OCW Test In Depth

 

POI- When performing the test you are looking for several targets with the same point Of Impact- the actual OCW will be the tightest group on the paper. But in addition to being the tightest group, it would have to also share its point of impact with the groups on either side of it.

OCW Example 1

 

 

 

 

 

 

 

Scatter Group-This will be one group of the round-robin sequence that seems to inexplicably open up. This is caused by a vibrating “Shock Wave”, as identified and described by engineer Chris Long. This is the point where the barrel is the most UNSTABLE. The OCW load is generally 1-2% (powder charge weight) higher than the scatter group.

 

Transition Group- a flyer which gravitates to the next changing point of impact. And if you look carefully, you will usually see that two of the shots are favoring or “pointing

to” either the previous or the next POI (point of impact), while the other shots trend the other way.

 

OCW Example 1 copy

 

 

 

 

 

 

 

 

 

 

OCW / Optimal Charge Weight- We are looking for the powder weight that will not be affected bychanges in;

Temperature, bullet weight, case weight variation, powder amount, primer, etc.

This charge weight is pressure/ velocity stable

  • (I personally had a load capable of a 1 hole – 5 shot group which was not stable.Sometimes you couldn’t miss, and other times it would send flyers everywhere. It shoots accurately about half the time out of my Marlin XL7 30-06, it does this because it is on the edge of the accuracy point in the load. )
  • OCW loads are tuned to be resilient to variation in components, and accurate in a particular caliber

(ex. Federal Gold Medal Match will shoot consistently from rifle to rifle)

  • ‘Dan shot an 1 ½ group with 3 cases (each with a different charge weight)!

He then shot a 5 shot group (⅔ MOA) using different primers, charge weights, and CASES. Some of the cases were 10 Grains heavier than the others.

You do not look for the smallest group!!! What we are after is consistency first, and then the group size second.

This is counterintuitive and you will have to force yourself to look for a PATTERN… not a SIZE of the group initially.’

Dan’s Website http://optimalchargeweight.embarqspace.com/#/ocw-test-example/4529811475

 

Reload ammunition at your own risk- never begin with a maximum powder charge, consult reloading manuals. I assume no responsibility for anyone’s reloading habits. You reload at your own risk.

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