“Audette ‘Ladder Load’ vs. Newberry ‘OCW’ Test Methods…”
This Week’s Tips or Tricks…
Note: all below CBTO measurements noted were taken using a Hornady Bullet Comparator attached to a Hornady Dial Caliper as shown below. Please also note that for all CBTO values documented below, I would also need to subtract 1.0035” from every CBTO measurement to get the corrected CBTO length.
Example: I measured CBTO with the Hornady Bullet Comparator attached to the Hornady Dial Caliper and noted the value as 2.8200”. To find the length that you will need to subtract for your particular tool to get corrected CBTO, close the Dial Caliper jaws all the way down with the Bullet Comparator Tool and the correct size comparator inserted and document the value of the Dial Caliper when fully closed, in the case of my particular tool this value was 1.0035” when fully closed. So to find corrected CBTO I would then calculate 2.8200” – 1.0035” = 1.8165” CBTO. If you are using a digital caliper, simply close the jaws and press the ‘Zero’ button on your calipers to achieve your corrected CBTO.
TIP: In one of my previous articles I introduced you to the exploration of a test called the Audette “Ladder Load” whereby we use a SWAG to give us a good Optimal Charge Weight starting point for our reloads and we will see how well those Ladder Load test results worked out. This week I want to introduce you to another method of finding the Optimal Charge Weight called the “OCW” test created and developed by Dan Newberry to be the “better mouse trap” for some…because a “Ladder Load” doesn’t always work and I am going to show you how and why they may or may not always work and also how an OCW test can complement or help to solidify your results…or as Mr. Newberry would argue, the “OCW” would be the better choice!
I am not going spend a great deal of time nor go very deep into the “OCW” test method as you can get a very in-depth understanding and explanation of the test by clicking on any of the blue links noted in the sentence above or hereafter which will take you directly to Dan Newberry’s www.ocwreloading.com website.
If you are completely new to the “Ladder Load” testing method concepts and/or the aspects of how to identify signs of pressure and dangerous characteristics when reloading, please refer to and read my prelude to this article by clicking on the following link where we go much deeper into the aspects of the “Ladder Load” and identifying unsafe and dangerous characteristics of your reloading practices:
Note: All of the referenced values, data, and/or observations noted above and hereafter are strictly dependent to the rifle, bullet, powder, primer, brass, and conditions in which this test was conducted. These results are all to be used as informational only purposes for you to see how the before and hereafter mentioned reloading methods can be applied to your particular reloading methods and practices and none of the following data should ever be used without proper understanding of metallic cartridge reloading and the exercise of safe and SAAMI compliant reloading practices and procedures.
First, let’s recap what the goals are and the types of data we are primarily targeting for by conducting an Optimal Charge Weight test or a “Ladder Load” or “OCW” test:
· Identifying where our optimal charge weight(s) starting point(s) may be…
· Identifying where our MAXIMUM safe charge weights may end…
· Identifying where charge weights may begin to produce HIGH PRESSURES…
· Identifying where charge weights may begin to produce EXTREMELY DANGEROUS PRESSURES…
· Identifying whether or not our firearm/brass/bullet/powder/primer combination was a good choice or if you may be “off in the weeds” with your components selections…
· Finding our best performing handloads in the shortest amount of rounds...
· Finding our best performing handloads with the least wasted development costs…
· We must ensure accurate and consistent results in order to avoid any “false positives”, so you should conduct this test with your firearm secured firmly into/onto a sled, tripod, or with a bipod/monopod
· For the best results when conducting a “Ladder Load’ test, you should conduct it at 300 yards if possible…
· For an “OCW” test, you can conduct it at 100 yards…
Next, let’s take a look at the (2) potential Optimal Charge Weights we identified in another “Ladder Load” test done with AR-Comp (target analysis shown below for reference)…
· Node #1 - ~21.7 gr. grouped around +/-1.00” vertical spread at 300 yds…
o This group had a good SD of just 10.3 fps and would allow us the tolerance of +/-0.3 grains charge weight variance and still hold our group size.
· Node #2 - ~22.4 gr. grouped around +/-0.50” vertical spread at 300 yds...
o This group has an even better SD of just 9.5 fps and would allow us the tolerance of +/-0.2 grains charge weight variance and still hold our group size.
o While this group has a smaller node for “error” with +/-0.1 grains less charge weight variance, this node does however provide ~90+ fps more muzzle velocity than Node #1 which is critical to help buck the wind in those longer range shots!
After we clearly outlined and analyzed ALL the data we had from that test we seen our final results were…
· MAXIMUM safe charge weight…22.9 gr…
· HIGH PRESSURES began to exhibit…22.7 gr…
· Node #2 at ~22.4 gr. grouped well at +/-0.50” vertical spread at 300 yds and additionally the powder charge did NOT exceed our MAXIMUM safe charge weight determined to be at 22.9 gr…therefore…
· OPTIMAL CHARGE WEIGHT...was determined to be ~22.4 gr which was under our MAXIMUM safe charge weight and incidentally also provided the least vertical spread of 0.50” during the 300 yd “Ladder Load” test.
· Note: previously in the other article we said a Ladder Load should demonstrate an incremental POI on the target such as climbing a ladder because we are increasing our powder charges incrementally thus increasing both the pressures and therefore muzzle velocities of each incremental charge weight tested also.
o PRO TIP #1: If you do NOT see any sort of noticeable vertical ladder rung stepping on your target, you may want to ensure your scale is properly calibrated and/or further examine all aspects of your reloading process to see where variations in your process may have been induced and therefore leading to the inconsistent and potentially erratic characteristics of the test results. However, note that if your meticulous inspection conclusion finds that no particular aspect was at fault, re-run the same Ladder Load test to see if results are consistent. If the results are consistently erratic, you have a rather definite conclusion that this particular “marriage” of components is NOT optimal and you should re-evaluate your choice(s) of components.
Once we had our Optimal Charge Weight of 22.4 grains of AR-Comp selected from the Ladder, we then proceeded to check our zero and group at 100 yards with (15) shots! As you can see from the bottom row of pictures in the above cluster, we ran (15) shots into a group at 100 yards and got a 1.179” Extreme Spread (ES) taking into account (3) pulled shots due to shooter error and a group size of just 0.770” Extreme Spread (ES) over the (12) Shots which excluded the (3) pulled shots. Now, when we identified the initial 22.4 grain charge weight from the “Ladder Load” test above, you can see above that the +/-0.2 grain variance gave us just 9.5 fps SD (see chart in top row, middle). So, after we had normalized all of our charge weights at the stable and consistent 22.4 grains charge weight…the SD came down even further to just 8.9 fps over the last (14) shots…the cold bore Shot #1 was a bit faster than all the follow-up testing shots….<--VERY IMPORTANT OBSERVATION TO DOCUMENT AND PAY ATTENTION TO HERE IF WE ARE ROUTINELY NEEDING TO BE VERY ACCURATE ON COLD BORE SHOTS SUCH AS AT A RIFLE MATCH WITH A COLD BORE BULLSEYE STAGE!!!
So that is all fine and dandy, not that impressive for a group size at 100 yards at just 0.770” ES with (12) shots and 1.179” ES with (15) shots. But let’s see what the results were when we stretched it out to 3x the distance at 300 yards!
On the second day we returned to the range but this time at the 300 yard line, we got the trigger man under control on the bang switch and I was able to shoot a (10) shot string at 3.041” ES…so just a pinch over 1 MOA at 300 yards…not bad, but still not good either because look at the huge shot disbursement for this group…sort of looks like two opposing armies preparing for flanking maneuvers with those two separations in the group.
Next, it was time for some magic! Watch what happened when we take a ‘mediocre’ group with a set charge weight and start optimizing it by tuning seating depth! In the target below, you will now see that by simply changing ONLY the bullet seating depth by -0.005” from the above target group seating depth…we reduced our group size to just 1.707” ES over an (8) shot string excluding (2) fliers…and a (10) shot group at 3.505” at 300 yards. Now, why the flyers? Yes it was me again, but this time low light right before dark pushed me to get this string off before we ran out of light and the range closed down for the day…damn short winter days!
I see one question already brewing in your mind…”why did you choose to back off in seating depth and seat farther away from the lands instead of closer to the lands?” The reason is because I know how this rifle reacts to other loads and it typically likes them backed off of the lands just a tiny bit farther. In this case I used my “Reloading DOPE” if you will to predict the most accurate direction of seating depth tuning to produce a better group for this particular load development combination. In fact, I may even see a bit tighter group size if I backed off just a tiny bit more yet. However, when you run this test, you may not know your rifle as well initially, so I would recommend loading one test group string at +0.005” and another at -0.005” from your initial seating depth and whichever way gets tighter…continue in that direction!
Ok, so the “Ladder Load” test worked pretty well…wouldn’t you say? Not bad for having a sub-MOA group within just a measly (24) round “Ladder Load” test string, (10) round 100 yard group string, and another 2-(10) round group strings at 300 yards to test seating depth totaling just a mere (54) TOTAL shots to achieve a sub-MOA group at 300 yards with a brand new load for an AR-15 rifle of all things (shown below for reference)!!!
Alright…now onto the “better mouse trap” as some may argue it! Many reloaders both new and old may already be working your load development scheme more like a modified version of the “OCW” test created and developed by Dan Newberry but you are inaccurately referring to it as doing a ‘Ladder Load’ test instead, shame on you…how dare you [LOL]! So, let’s identify the difference and see how a true “OCW” test is really conducted per its creator and how dramatically it differs in execution compared to a “Ladder Load” test.
Using our Broken Box R LLC “Charge / Seating / Tension Tuning Test Target” and data tracking sheet, we will layout our load development test charge weights in ~+2%invervals from the Minimum Suggested Charge Weight for this load (in this case we will just move up by +0.3 grains incremental charges (i.e. 20.5, 20.8, 21.1…) for the simplicity of illustration within this article. Now, you will load (3) rounds at each of the designated charge weights and clearly mark and place them into your reloading box…NOTE: it is very important that you keep EVERYTHING the exact same from (3) round test string to (3) round test string accept the incremental jump in the powder charges to be tested! Once you have (3) rounds for each of the test strings, in the case of this “OCW” test we have (9) strings, you are then ready to hit the range (see below data tracking sheet for illustration on each of the (9) strings to be tested). Note: you will also want to load up an extra 1-2 rounds at each of the designated charge weight intervals in case you have any fliers and need to re-shoot one of them in order to achieve a (3) shot group…but do NOT mix charge weights when re-shooting any of your fliers, ensure you are shooting the proper extra for that particular charge weight string!!!
After you make it to the range, you are going to set up your target and start shooting your “OCW” test in the following manner in round-robin tiers as illustrated below. You will start with the Tier #1 String and move through all (9) test charge weights, then start over back at the beginning of the Tier #2 String and continue so on and so forth until you have shot at least (3) good rounds for each of the (9) tested charge weights as we had in the case of this test. Ensure you allow your barrel to cool in between each of the fired shots and strings.
After completing this entire “OCW” test process above of tiered round-robin style shooting at all the designated charge weights…per Dan Newberry’s method, you will then triangulate each of the group’s centroids and find (3) adjacent groups that have the most similar Point of Impact (POI) in relation to the bullseye of the target using said centroids. So what does this look like and mean?
Throughout charge weights 20.5, 20.8, 21.1, 21.4 and 21.7 grains the centroid POI continued to oscillate about the center axis of the bullseye as seen below. Once the charge weight reached 22.2, 22.4, and 22.6 grains, the centroid POI became relative to the same spot in relation to the bullseye. Then at 22.9 grains the POI began to oscillate again also shown below.
Now that we have found (3) adjacent POI centroids in the same relative position to the bullseye, we would then determine the median point of those particular charge weights tested…which in this case would be 22.4 grains…and now you have just determined your Optimal Charge Weight per the Dan Newberry “OCW” test method for this particular load development test. Note: obviously the below illustration is a ‘simulated’ course of fire only as I was unable to conduct a live course of fire using this method prior to writing this article; however, I do plan to visit the range within the near future with this very same load development combination as ran above using the “Ladder Load” test and compare the actual live fire results to that of the “OCW” test method for determined Optimal Charge Weight and see how they both agree/disagree!
What do we do now that we have established our initial Optimal Charge Weight from our “Ladder Load” or “OCW” test??? Now you likely have a bit more load development ahead of you to begin optimizing seating depths, tweaking your case prep practices to reduce runout, crimp, neck tension, shoulder bump, and so on and so forth in order to find that very best 3/5/10 shot grouping that this particular load and firearm is capable of producing at a given distance.
Alright, now that you know what the procedural differences for each of these two methods are…let’s take a closer look at where each testing method may be better suited or less adequate. First, before anybody decides to just hop up on their broom stick and fly off the handle about the way I may have classified any of these factors per the designated test method(s)…understand, this is my professional and analytical opinion in regards to these classifications. I have attempted to remove any favoritism or bias from this breakdown and favored neither in their aspects of my opinions…because the fact of the matter is that I use both of these methods routinely, but tend to lean more heavily toward using the “Ladder Load” method primarily because it is a quicker and easier setup process for me and I am very meticulous in the detailing of my reloading data capturing and analysis aspects anyways. If you are a data junky like myself and the analysis part of taking the “Ladder Load” to the “nth” level like I do above doesn’t bother you, then give the “Ladder Load” method a shot! If you have no desire nor patience to “nth” it…you will want to take the “OCW” test method route! If you have any further questions or comments regarding this article or its contents, please feel free to email us at firstname.lastname@example.org.
So what is the moral of this story
folks...there IS indeed more
than one way to skin this cat and you should ALWAYS access ALL relevant data
and conduct a thorough analysis BEFORE establishing a basis
for your conclusions. Doing so will keep
you on target and SAFE to shoot and reload yet another day!!!
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Do you have a Tip or Trick regarding reloading that you would like to see posted? Please send us your Tip(s) or Trick(s) and we will see about getting them posted!
Written By: Kyle R. CEO of Broken Box R LLC
Copyright © 2017 Broken Box R LLC – All Rights Reserved
This article was first published on February 17th, 2017.