opinions on ladder test and groups...

[chrismc]

Well, after reading about it for a year, curiosity got the best of me and I did a ladder test... I did find the node (I think)as expected (400yds) and then tweaked it with finer loads that shot well in the node. I did 8 shots up the ladder, 8 down the ladder, and finally 8 up again.
Previously I shot many many dozens of groups to find my best load - and to my amazement, my pet load from shooting groups was only a 1/2 gr away from the middle of the node!

Here is what I found in words - first off, the caliber was 325wsm and 4007ssc powder...also, I went up in 0.3gr increments.

Anyhow... at the range... relatively light crosswind... the lower end of my 3 step ladder test was wacky - like at 400yds each bullet hole formed a triangle with 1 ft sides... 0.6 gr later, it was 6" horizontal, and 3" vertical, the next group was a 4 inch group (again, slight vertical spread, and 4" horizontal) but 6" away from the previous good group... then another 0.6gr and the shots went wacky again! So I went home, loaded a few rounds which gave me the tightest 'spread' on the ladder, and hit the range the next day.
What confused me is the two loads that showed real promise were spaced apart, not tight like I have seen other ladder tests... despite this, they had the least vert spread, and the best groups.

On to the range again - Viola! fired the 64.8gr 3 shot group, then the 65.1 gr 3 shot group, both at 200 yds. I was left with 2 nice 1 1/4 groups. Here is what blew me away tho - the 64.8 was dead center but 1.5" low of the bullseye at 200... the 65.1 was 6" high and 3" left of the same bullseye. Sooo.... then i fired 6 rounds at another target - one 64.8 then a 65.1, then a 64.8, then a 65.1, etc...you get the picture... What I found was the same - one nice group below the bullseye, and another nice group up and to the left again...

So i am curious what you guys think may cause such a change in the POI with 0.3gr increment in powder??? Maybe I didnt find the node after all?

So the 2 lessons learned to me was that there can be a real fine line between a great pet load, and one that is mediocre at best - and (2) that each load has a different POI!!!

Please share your opinions!

Chris

 

[horseman2]

The barrel was in a different whip position when it spit those puppies out.
I am sure most have experienced this phenom.
Are you at Max pressure? or are you where you want to go?
Load the one with the highest powder charge and move your sights.

No problem

 

[chrismc]

Not at max pressure, about a grain and half below where the primers were cratered... the puzzling thing is I thought the node would have the groups close to the same POI, but they are not... makes me think I havent found it, but to answer your question, yeah I guess i am where I want to be with good groups!
c

 

[deadeyes40]

i would either sight in the 64.8 grain loads or try some loads with 64.6,64.7,64.9,65.0 they might even shoot better.i found the same thing with my test loads.a change of .2 grains in my 222 rem would change POI as much as 5-6 inches.still decent grouping but the POI was different for just about every load.i even found that just because you increase the powder charge doesn't mean POI will be higher,have seen a.2-.4 grain increase drop POI as much as 4 inches.

 

[Rory McCanuck]

It sounds like you have found the "scatter node".
ht tp://optimalchargeweight.embarqspace.com/#/ocw-vs-ladder/4529811360
Dan Newberry came up with his "Optimal Charge Weight"
and finding it requires a variation of the usual ladder test.
and outlines his method here:
ht tp://optimalchargeweight.embarqspace.com/#

Some very interesting reading there.