I'm working up my first loads for my .308 bolt gun. Aac-Sd .308 with 168 gr smk ,fc brass ,varget and imr 4895. Do I just shoot 5 shot groups to see what works the best? Hodgdons data and my Lyman manual start at 2 different load numbers, which one do I go with?
ladder test for .308 loads
- Thread starter Truth223
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Ladder test is one round at each powder charge weight. But you need a fairly long range. You look for 3 rounds in a row that are close vertically.
OCW is 3 round groups shot in a round robin. One round each charge weight, then repeat. You are looking for 3 groups that print to the same point of impact from the the point of aim. 3 groups that print at say 1 o'clock from POA.
For both, then repeat with smaller charge weight increment in the range of the 3 groups you pick.
OCW is 3 round groups shot in a round robin. One round each charge weight, then repeat. You are looking for 3 groups that print to the same point of impact from the the point of aim. 3 groups that print at say 1 o'clock from POA.
For both, then repeat with smaller charge weight increment in the range of the 3 groups you pick.
When I did a OCW test on my AAC I started with 42.4 IMR 4895. Loaded 3 each 42.4, 42.8 43.1. Second round I fined tuned around 42.9
It's not that hard to wrap your head around. You just have to realize there are 3 shot groups and better yet 5+ shot groups. There is the OCW test which uses 3 shot groups to find a similar POI. You can add the round robin approach to OCW to spread human error/environmental changes over the whole test. Then there is the Ladder test. The ladder I think is probably the best choice for long range load work up. You can find a load with it that will have less tendency to change over environmental differences, will be more consistent and it takes less reloads to find it.
For the appx. 45 bullets it would take to do an OCW test you could load up appx. 30 bullets with varying charges for 2 ladder tests. If a node exists on both ladder tests then you are already close to what you want. Pick the middle of that node and load it up plus a couple grains above and below and check 5 shot grouping at 100yds. Do at least (2) 5 shot groups per charge in case of shooter error. Pick the one that's the best per speed/accuracy/repeatability, reload and go shooting.
Some people like OCW some like Ladder testing. It's kinda like Ford vs Chevy I guess.
For the appx. 45 bullets it would take to do an OCW test you could load up appx. 30 bullets with varying charges for 2 ladder tests. If a node exists on both ladder tests then you are already close to what you want. Pick the middle of that node and load it up plus a couple grains above and below and check 5 shot grouping at 100yds. Do at least (2) 5 shot groups per charge in case of shooter error. Pick the one that's the best per speed/accuracy/repeatability, reload and go shooting.
Some people like OCW some like Ladder testing. It's kinda like Ford vs Chevy I guess.
The ladder test in the stickies explains it rather well and includes pics. It's more for a master behind the trigger and a minimum 300 yard range though. I don't have the skill nor the range to do it properly so I'm just gonna shoot 5 round groups .2 apart and go from there.
There are really only two things to remember. One is that different charges cause the barrel to flex differently and second, you want a charge that causes the bullet to leave the barrel at the most efficient "harmonic".
All the single charge ladder test does is identify the different "harmonic nodes" or where the barrel seems to naturally want to be when the bullet leaves. That's why you will see groups where each bullet had a far different charge weight.
Ideally, one uses the old Creighton Audette Ladder test of one shot per load, and then verifies it with a fine tuning session using 3-5 shots per charge which then is only varied by a couple of tenths above or below the loads identified in the ladder.
You could accomplish the same thing if you merely took the starting load for any given caliber/bullet/powder combination and then shot 3-5 shot groups, increasing the load by .2 gr until you found the magic group or maxed the load for the powder. That would take far more components than the ladder, OCW, or combination of both to reach your goal.
Just like every car seems to have a speed it likes to travel on the freeway where it feels best, doesn't seem to be straining, and perhaps gives the best fuel mileage, same for rifle loads and accuracy.
OK, Ill be testing my 6 Creed by loading up 41-43grs RE17(5 shot groups) in .5gr increments, Ill be shooting at 300yds. Is there anything wrong with this approach? For the guys that do the ladder test, do you reload at the range?
