Modified Ladder Test

[cowtownup]

Just starting loading using IMR-4064 under 175 gr. SMK's...

*I loaded 5 shots each at half grain increments starting at 40.5 and going up to 42.5.
*I shot these round robin style as not to be partial to any one particular load and no cleaning was done of the bore during the test.
*I had zero'd my rifle with a different round so my POI was off some from my POA each time, but regardless I kept the same POA for each shot with each particular charge weight.
*I shot 5 shot strings and allowed about 10-15 minutes in between for barrel cooling.
*Shooting at 100 yards.
*Shooting off of a bipod on the front and bag on the rear.
*I'm shooting a bone stock Stevens Model 200 in 308.. Nothing special, just trying to learn so that when I do build a shooter oneday I'll know how to work up a load for it.
*I can't say for sure where shot 5 is on 41 and 41.5 grain loads, but I feel like they went thru and existing hole. (???)

Help me learn as much as possible from this test.

What do you see?
What would you do next to dial in the load?
Do I need to looking for less vertical stringing or just the best grouping of the 5 shots? (at this point)

 

[jwrowland77]

Me personally, I would keep going up to the max.

You see how your groups started tightening up? Keep going and see if it tightens up even more. You have max of 44. If you go look on the Hodgdon website it goes even higher into compressed loads. This is why it's always good to look at multiple sources. I recently did a workup using same powder and bullet.

 

[oldfortyfiveauto]

Here's my version of ladder load to help you decide what to do. I shoot one round at each point. Notice shots 1 through 4 have very little vertical change. The last 4 start moving vertically with each shot. In this case I would load some at 29.3grs for groups. I've had pretty good luck ruling out bullet/powder combinations with only 8 shots, assuming I do my part shooting. In this case I have +/-.3grs tolerance to work with....no reason to weigh each charge with that tolerance.

I usually try to shoot this at 200yds. I've found the grid really helps read the target.

 

[WestKentucky]

Cowtown, your close to optimal load. Group is tightening but it's getting right. I would back my ladder off a bit. You went in "rungs" of .5 gr. I would start again at your "top rung" and try it again with .2 gr increments if you really want to dial it in. To go to the tenth or even hundredth is great, but your talking about very tedious work and amazing scales and tricklers at this point. Good shooting.

 

[WestKentucky]

Old 45, notice the holes on the target too. Torn vs cut...usually not so obvious on a ladder test.

 

[oldfortyfiveauto]

Pretty normal for plain copy paper.

What's being overlooked here is that the point of a ladder load is to find the sweet spot for a powder/bullet combination that gives a wide tolerance on powder weight so you don't have to weigh each charge. In this case with my new 204 Ruger I run 4 powders and only two showed a sweet spot. I've since loaded them for groups to confirm. CFE223 and Benchmark were the winners with the edge going to Benchmark running under 1" at 200yds.

 

[spitballer]

Like your methodical approach and agree with "round robin" alternating of charges - I do same.

 

[cowtownup]

I think I'm going to load some up at 43, 43.5, and 44 and see what they do before I go any further. I understand what old45 is saying regarding the real meaning of a ladder test and the wide powder charge range, but I'm more in search of a good consistent load. Its really time consuming when your doing these with a sporter barrel cause they heat up FAST... My ultimate goal with this rifle is to shoot out to about 500 yards and learn about working up loads, get some trigger time while doing it and hopefully work on calling some wind and ranging targets.. Thanks for the help so far.. Much appreciated...

 

[oldfortyfiveauto]

The key to a consistant load is finding the powder/bullet's sweet spot with the biggest tolerance. If you are not in the sweet spot then everything must be pertect every time. I don't know about you, but perfection is pretty hard to maintain. I've not found a rifle yet that did not have a sweet spot combination. When you start loading for a prairie dog hunt then you will really understand the importance. Weighing every charge gets old fast on 500-1000 rounds

 

[Comrade Mike]

Try this. I load in equal increments to the max load. Generally I get two powder charges that will shoot really well. Then next ladder go between those two points in smaller increments. Eventually you get this.

 

[kelbro]

I think that you will probably just be wasting components if you keep going. 42.5 of 4064 has worked very well in every 308 that I have ever fired it in.

 

[Dave P]

What I see is that the 41 group is the tightest; it has the least vertical spread. Horizontal spread is operator error.

And you should be doing this at 2-300 yards really.

"the point of a ladder load is to find the sweet spot ... that gives a wide tolerance on powder weight" Roger that.

 

[spitballer]

Agree with last post. Vertical spread is key factor for me also.

 

[cowtownup]

Okay I worked on this again today. Since 41 grains looked promising in the last test I tried it again. I also went up and tried 43, 43.5, and 44 grains. I moved the test out to 200 yards as mentioned but I went with 3 rounds of each instead of 5 like in the previous test. The weather was similar however the wind was up some.. I had cleaned the bore after the last test so I rezero'd my rifle with a few fouling shots to start with. Lets take a look...








41 grains @ 3.0" vertical spread
43 grains @ 2.6"
43.5 grains @ 1.8"
44 grains @ 2.4"

It appears 43.5 grains is where my best vertical spread is. I guess I could go on and on with testing this load but for my bone stock rifle, I think this should do. I appreciate any constructive criticism. I did notice that my adjustable objective moves each time I shoot. I have to readjust it after every shot to get better focus on the target. I bought this scope used and I guess that is why... Thanks again for the help...

 

[Andrew Leigh]

Wrote you a long post that somehow has ended in cyberspace.

The long and short is google Dan Newberry- OCW. Essentially you are replicating his method. He gives a very nice write-up that may well assist your in your method, especially how to interpret results.

 

[Centurian22]

Andrew beat me too it. Definitly look into the OCW method. If my understanding of a 'ladder test' is correct you are doing something completely different and as mentioned, much closer to the OCW work up. In a ladder test one round is loaded at each 'step' and all are fired at the exact same POI. The shots will 'string' vertically as charge weight increased but you will see 'nodes' as groups and in some cases a higher charge weight that actually shoots lower than the previous step.

When I started working up my .308 168smk with IMR4895 I used a ladder test (as discribed above) AND separately an OCW work up. Results from each test both helped point to two matching/similar accuracy nodes that I will be doing further workup on.


http://www.thehighroad.org/showthread.php?t=733309

 

[spitballer]

Thanks for sharing target. I've pored over many such groups, crunching the numbers off the chrony and planning my next batch. Interesting that the smallest charge would throw the bullet up so high!

These targets are always easier to decipher when accompanied by chronograph numbers. Did you by any chance run a chronograph with this target?

 

[cowtownup]

I have not added a chrony to the mix yet but I certainly want one really bad. The only muzzle velocities I have to go off of are in the loading manual... I decided to go with the 43.5 grain load for my first batch and once I start shooting those I can usually back into the muzzle velocity using my ballistics calculator. I know thats not the most accurate way to do it, but it works for now...

It is interesting that the smallest charge results in a higher POI... I've noticed that once in the past, but kind of brushed it off...

 

[WestKentucky]

You can calculate velocity by bullet drop. The acceleration of an object due to gravity is 9.8m/s^2. So take your shot at your max height (peak of bullet arch, typically about 55 yards on a 100yd zero or 115yd on a 200 yd zero. Then tak it at a longer range (double your max or more) measure vertical change and start using match to cancel variables until you are left with ft/second. It won't be dead on accurate, but it will get close. The trick is being consistent with numbers. Convert all measurements to meters before you start the math.