Deciphering ladder and next steps

[tony d willIiams]

Load between 4 and 5 then work your seating depth. Put those 168s in the lands, I have never tuned a rifle that shot its best jumping past .010".

In my limited experience I have found that changing the seating depth changes the pressure radically, whether seated too deep or too shallow. Once the seating depth is proper then I do the ladder test should be performed. Groups are not as important as the vertical consistency of the three shot groups, not to worry about wind at this time. I start with large differential, 0.50, of powder changes in my 338 LM. Then I narrow it down to 0.10 differences to refine it.
I am testing the major, minor differences when components are changed, brass, bullet, powder and so on. With time I plan to become closer to a man with knowledge.

 

[parshal]

I would shoot a few groups with 60.8, between load 4 and 5 simply due to the low SD. I'd want to see if that SD stays that low and how it groups. For BountyHunter, is that not a "node"?

I'm honestly trying to learn here with my question. Alex seems to have come to the same conclusion I did with between 4 and 5 being a good place to start. Load 2 has a good SD but it's smack in the middle of two higher SDs. I would think one would look for the best SD in an "SD node" like 4 and 5 and then verify it would shoot?

 

[BountyHunter]

I would shoot a few groups with 60.8, between load 4 and 5 simply due to the low SD. I'd want to see if that SD stays that low and how it groups. For BountyHunter, is that not a "node"?

IMO it is not. Look at the spread of mv between 2 and 3 compared to 4 and 5.

You are looking for close impacts AND mv spreads. 2-3 rds will group with close mv and then make big mv jumps of 20-25 fps routinely to the next mode and then you will get the close impacts and mv again.

 

[Alex Wheeler]

Ladders can be tough with sporter barrels. You just cant put a lot of rounds down them quickly with out them getting too hot. I do a 3 shot ladder, witch is just 3 shot groups all at the same poa. 3 shot group, cool, 3 shot group, cool, ext. The reason is your getting data from the groups as well as how they plot on paper with is possibly more important. I do them at the farther distance I want to shoot the rifle, usually at 1k. Your load will become a lot more obvious at 1k than at mid range. But one thing that most rifles do (when increasing powder charge) right after they shoot their smallest group is shoot a big one, usually with a large change in poi. 6 is the big one and it moved a lot...

 

[tdot]

From looking at the ladder, I would focus on 3. From looking at the SD/ES, I would have thought 4 or 5. I haven't personally found amazing loads where the vertical string and low SD/ES don't match.

Depending on your needs I might try another bullet or powder before spending a ton of time on this combo. (Of course if it's a short/medium range hunting round, its might be plenty good)

 

[Saracen]

I'm learning a lot from this and like the concepts.
AND I have something to offer that I see no-one mentioning. That is headwinds/following wind effects. It has been absolutely amazing to me to see how much these affect vertical shot placement. If ladder testing is all about vertical, then this a variable to be controlled. Headwind seems to raise POI (point of impact), while tail wind lowers POI. Ignoring these can drive one batty at long range!

Just another (like we needed more, eh?!) variable to watch.

Jim Irwin
Central Texas

That's yet another reason not to give ladders 100 % credibility.

 

[Almondgrower]

IMO .....More often then not a factory rifle can show some vertical stringing due to bedding issues . That vertical stringing could drastically impact the ladder test results pretty much making the ladder test info useless . That is why I asked about the rifle in a previous post. Custom built rifles normally show the most credibility during a ladder test. If you feel this may be a possibility, then maybe OCW round robin style test may work better