Ladder load development testing.

[skipper]

Every wonder what the best load for your rifle is? You can find out using a ladder load development test. This question comes up from time to time on this forum and has been discussed extensively in the past. Your rifle is unique, there are many like it, but yours likes what it likes and doesn't follow any particular rules just because of brand and model. I'm going to kick off this subject for the newer members with the little knowledge I have gained. AND I do mean LITTLE! I am not an expert, but I'll share what I know. Please, be kind!!!

A ladder test is a method of testing a load combination using progressive charge weight increments while looking for a group of shots with the smallest points of impact (POI) measured center to center. You are trying to identify a "sweet-spot" in the barrel harmonics by using the bullet's impact on the target.

For optimal results, during the test, all variables must be kept to an absolute minimum with exception to the actual powder charge weight. For example, the same powder, bullet, primer, case, seating depth and barrel temperature must be maintained throughout the test. Only the powder charge changes by a predetermined increment during the test. If more than one variable is changed during the test it is almost impossible to determine which variable caused the change in results, essentially nullifying the test.

More to come!

[Tom Kat]

Thank you for starting this thread, I will read all of it with great interest.

[Bill K]

Super fine explanation of what and how to begin and think about a ladder test, for YOUR rifle. Skipper gives a fine comment and how to begin and proceed. Follow it and be safe and sound, again with YOUR rifle and loads. You will find it's sweet spot.

[Rick in Oregon]

Excellent subject matter.

I'll add that when you do a proper ladder test, when complete, you'll really know what your rifle likes and doesn't like. It gives a very satisfying feeling that you've "done it right", and the load has been found.

No mystery, it just takes time, patience, and some expenditure of components. But it IS worth the effort!

[skipper]

*Ladder Test SAFETY*
First bit of ladder testing advice I’m going to give you is to get a Reloading Manual and follow the load data TO THE LETTER. For this discussion I will be referring to the LYMAN 50TH EDITION Reloading Handbook. No, it’s not the only reloading handbook but just the one I am going to use for this discussion.

Component Safety
Primers - Next, lets discuss small rifle primer safety. Small Rifle Primers are separated into two groups. Those that are designed for moderate pressures (40,000 psi) and ones that can handle higher pressures (55,000 psi) normally found in the 204 Ruger. Primers, that have a thicker cup, are designed to safely operate at higher pressures include the CCI 450, CCI BR4, Fed 205M and Rem 7 1/2. See the table below. The thinner cupped primers may very well exhibit sign of high pressure like flattening or bursting through at the firing pin contact point. ONLY use the thicker cupped primers in yellow.

.

SRP.jpg (30.11 KiB) Viewed 1966 times

.

Powder – Later I’m going to walk you through how to load and then shoot your ladder test. For now, choose a powder that is readily available to you. Paying the Haz-Mat fees to have it shipped gets expensive quick. I digress. The point I’m intending to make is to stay within the Burn Rate range suggested in your reloading manual. Venturing out into unpublished load data can cost you a rifle, an eye, etc. We are going to start loading five rounds each at the very minimum published load data and incrementally work our way to the maximum in .2 grain increments. That DOES NOT mean you have to shoot every group of five you load. Anytime, during the firing process, you discover high pressure warning signs such as a bolt that is harder to open, or a flattened primer, or case head expansion, or the imprint of the ejector hole on the case head it’s time to STOP!!!

The powders listed for loading the 39 gr. Sierra Blitzking are: (largest projectile I would attempt in a 1:12 twist)
RX-10, 2015, H-322, IMR-3031, Benchmark, H335, X-Terminator, 2460, IMR-4895, and Varget

Just FYI, The 39 gr. Sierra Blitzking is reported as very accurate in a variety of rifles here on this forum. That doesn't mean your rifle will like it, but definitely worth a try.

[skipper]

Now that you have selected a powder it's time to start reloading. Remember, you are trying to reduce or eliminate variables with the exception of powder charge. Speaking of which, if you don't have a digital scale you should consider buying one. We have selected the 39 gr. Sierra Blitzking already. To remove a variable, make sure you have enough bullets (35) from the same Lot Number for the test. A minor amount of weight sorting would be in order here. Stacking the bullets in order from the lightest to heaviest will reduce the weight variable to some degree.

I want to use Benchmark since it will fill the case to the 90% mark. Try not to select a powder that results in a compressed load. I'm going to start by loading 5 identically prepared cases with the minimum charge, which is listed as 24.0. I'll select the CCI BR-4 primer from the list above. All primers should come from the same lot number. Next I'll fill another 5 with 24.2 gr of Benchmark. Then another 5 with 24.4 gr. of Benchmark and so on till I reach the maximum charge of 25.2. That's a total of 35 identical cases now sitting in my loading block separated by charge weight so that I don't confuse them. A colored permanent marker can help. No need to reinvent the wheel here, there is a great article on case preparation over on 6mmbr.com:

https://www.6mmbr.com/JGcaseprep.html

Now we can seat the bullets using the given OAL of 2.260". Use a quality seating die that is known to produce the least runout possible. You might learn that your seating die isn't very good like I did when one of my freshly seated rounds fell over and started rolling across the table. The tip wobbled so much it wasn't even funny. If you are reloading for an AR or other magazine fed rifle you might have to adjust the seating depth to fit. It is important, however that you seat ALL rounds to the same length. If you know enough about reloading to use a comparator, by all means go ahead.

GOAL of the test:
When you shoot your ladder test you are looking mostly to identify the group with the least amount of vertical spread. Horizontal spread could be caused by the wind so the vertical spread is more important. Think about it, as the powder charge increases the Point of Impact on the target should rise vertically. You will find a sweet spot where the vertical separation is minimal. You may also find that there are more than one NODES where the bullets come together. I would choose the NODE with higher velocity over the lower.

Lets discuss the actual shooting process in more detail later. Time for dinner.

[skipper]

Shooting Groups for the Ladder Test

So, now I have 35 rounds loaded into 7 groups of 5 rounds each from the minimum to maximum powder charge in .2 grain increments:
5 @ 24.0
5 @ 24.2
5 @ 24.4
5 @ 24.6
5 @ 24.8
5 @ 25.0
5 @ 25.2

Next, I want to make sure my rifle is clean and lubricated. No carbon ring in the throat of my chamber or copper fouling of any sorts. Now I going to gather up all the gear listed below and head to the range on a day with favorable conditions for shooting bug holes. A stable shooting foundation is essential at the range. A Caldwell Lead Sled or a front rest and rear bag are preferable. If you have a bubble level on your scope, use it to make sure the rifle remains cant free at every shot. My intention is to shoot all my groups of five in order from smallest charge to heaviest. I’m going to change targets in between each group of five making sure to record the charge weight on each target. Monitor barrel temperature throughout the string of fire.

Gear List:
Ladder test rounds (35)
Cleaning rod
Bore/Chamber brush(s)
Bore guide
Bore Cleaner (insert your cleaning solution of choice here)
Patches
Extra rounds (for fouling/warming)
Target(s)( use a separate target labeled for each charge weight)
Stick-on Bullseyes
Staple gun
Chronograph
Bags/rests
Safety glasses
Ear plugs/muffs
Calipers
Range Book
Pen/pencil
Scratch pad
Water
Sunscreen/Hat
Thermometer
Anemometer
Spotting scope
Ruler

At the range-

Info to record:
Date, time, weather conditions, barrel temperature throughout test, any shooting inconsistencies. (if you pull a shot, add an asterisk) Keep good records and label everything.

Bench setup:
Use a front rest and a rear bag if possible. Your setup should be very firm if done correctly. Rifle should slide back in the bags and return to battery easily. Eliminate rifle cant and level as possible. Rifle cant alone can ruin the whole test. Place your rounds and range book on the right side of your bench if right-handed. You’re trying to setup a mini field laboratory suitable for testing.

Target setup:
The target should be a measured distance for proper ballistics calculations. Most likely 100 yards. One bullseye for every group of five. Target square and level. No shadows.

Barrel temperature
Use fouling shots to heat up the barrel and condition the bore. Regulate barrel temperature allowing adequate time between shots. Changing targets between five shot groups can help keep temperatures under control.

Accuracy:
You must maintain accuracy during shooting so that the test results will have value. Take your time, make every round count. Be breath and trigger control conscious. Check barrel temperature after each group of five shots. Don’t focus on the shot holes, focus on sight alignment and sight picture. Post shooting analysis of groups is best done at home. Your pet load should make itself known. If not, choose another powder bullet combination and start getting ready for another ladder test.

Further development:
Once you have found the PET load for your rifle you may be able to improve it by varying seating depth or neck tension. Just adjust one variable at a time.

[Tom Kat]

That's the best testing instruction I have ever seen. Thank you for the level of detail I needed.

[Tom Kat]

This was interesting to me, and something I never thought about- "When you shoot your ladder test you are looking mostly to identify the group with the least amount of vertical spread." I am guessing that the ladder test would even out on a load when you found the right charge. I had one load with my .223 that looked good but had some vertical stringing. I thought maybe it was an issue of the stock touching the barrel. I am going to reproduce that load, but in the increments described about, and see if I can find the sweet spot.

That was a really good post, something for me to build on.

[skipper]

A chronograph can really help with that. You may find that there's more variation in velocity than you realize within the same load.

[Tom Kat]

I may get one eventually. This spring I have an upgrade that will be documented with pictures. A concrete slab and a new to me bench.

[Rick in Oregon]

I may get one eventually. This spring I have an upgrade that will be documented with pictures. A concrete slab and a new to me bench.

TK: You may want to consider the Shooting Chrony chronograph. I've used them for over 25 years with perfect results. The basic model can be had for about a c-note, models with more features run under $150. I cannot stress enough how important a chronograph is to a serious handloader to find that Pet Load.

Also, once you've arrived at that Pet Load, with the aid of a ballistics program (free online), you can make up "Come-Up" charts for each rifle and it's preferred load. I print mine out and affix it to the ocular scope cap for easy reference. Laser range the target, consult the chart, allow for wind, hold dead on and fire. It works, and works very well.



That particular chart is on my Cooper M38 chambered in .20 Vartarg and is used to 500 yards on ground squirrels and rock chucks.

None of that is possible without a chronograph. You need one to get the best results possible from the rifle and you.

[Tom Kat]

I could see getting one some day.
Your drop chart idea is pretty cool, way better than relying on memory.

[Tom Kat]

I am not familiar with that caliber but it looks like a flat shooter.

[Bill K]

Tom Cat... You should check out the 20 VT.. Everyone should own at least one with a 1/11 twist barrel. Amazing shooting cartridge. And even the improved version of it. ( 20 SCC )