338lm Ladder results

[timelinex]

to make a long story short.. It was a 1.5 mile hike with 50lb of stuff on my back, through the 105 degree desert to get to the shooting location. A combination of wind constantly knocking over chrono, fatigue and bad testing conditions led me to only do one single ladder and pack up and hike home( or to the car rather). I think I'm gonna have to redo my testing, but It looks like there might be some useful info with this ladder in combination with my pressure testing range report from another day.

The ladder is ~650yards.
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These were the velocities
90gr:2689
90.4gr:2746
90.8gr:2702
91.2gr:2726
91.6gr:2745
92gr:2745

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Here are velocities from a week back when I was doing pressure testing at 100 yards:
90gr:2753
90.5gr:2712
91gr:2702
91.5:2741
91.7:2744
92:2752
92.3:2756



The load is:
HSM once fired brass
300gr bergers seated to Mag Length
H1000
fed 215m

<span style="font-weight: bold">My analysis:</span> There is Definitely something funny going on between 90-91gr. In both tests the velocities are VERY erratic. It doesn't show up too much on the 100 yard test, but at distance you can see the velocities separating the POI.

Now it looks like there is a definite node at 91.4-92gr. The POI spread on both the 100 yard test and the 650 yard ladder were very tight and the velocities were all within 10 fps of each other!


So from the limited data that I do have, it looks like there is a clear scatter node and clear accuracy node. Both POI and velocities back it up. HOWEVER, it is in fact limited data which is whats bothering me.. So what do you guys think? Should I load up a 3rd round for all the charges and do this again in better circumstances, or should I start refining the node??

 

[turbo54]

Re: 338lm Ladder results

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: timelinex</div><div class="ubbcode-body">
The load is:
HSM once fired brass:
300gr bergers seated to Mag Length
<span style="font-weight: bold">Varget</span>
fed 215m

</div></div>

Varget?

 

[timelinex]

Re: 338lm Ladder results

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: timelinex</div><div class="ubbcode-body">
The load is:
HSM once fired brass:
300gr bergers seated to Mag Length
<span style="font-weight: bold">Varget</span>
fed 215m

</div></div>

Varget?

</div></div>
Good catch! So used to using varget in my 308, I meant H1000

 

[MALLARD]

Re: 338lm Ladder results

ya refine the load. For me, when i find a node, i can usually have a few grains of variation , ( like .3) and still exit at a node, so your charge weights between 91-92 seem to support that.

 

[timelinex]

Re: 338lm Ladder results

Thanks for the reply. I think I decided with doing that as well. Gonna load up 8 more rounds with 91.6gr and see how it does over the chrono and grouping at a distance. Even with the limited data, the results look too obvious to ignore, if it doesn't turn out as good as I expect I can always start over.

 

[B3dlam]

Re: 338lm Ladder results

You could look at doing another ladder from 91.2-92gr at .1 gr increments so another 8 shots then fire the ladder again and see the best 3 rounds in that group and use the middle one from that?

 

[timelinex]

Re: 338lm Ladder results

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: B3dlam</div><div class="ubbcode-body">You could look at doing another ladder from 91.2-92gr at .1 gr increments so another 8 shots then fire the ladder again and see the best 3 rounds in that group and use the middle one from that? </div></div>

Everything I have read has said that the 338LM doesn't reslove .1gr differences. It would be like a 308 resolving .05gr

 

[timelinex]

Re: 338lm Ladder results

I had some strange results... The remaining 91.6gr rounds that I loaded before to do ladder testing grouped great and had close velocities. But a new 5 rounds that I made, to supposable the same exact spec but just a week later, had insanely fluctuating velocities (2730-2780) and grouped bad. Hmmmmmmmmmmmmm

 

[cali_tz]

Re: 338lm Ladder results

one has to use some statistical methods to trying to quantify what are essentially random (in the statistical sense) variables. You can not conclude anything by running one of each load. You would want to run at least 5 of each load, at the same time chron each shot while shooting for ladder accuracy.

Regarding 0.1 grain differences, I have no idea what you mean by 338lm can't resolve differences of 0.1 grain, but I can say that even with measuring each load to exact 0.1 grain desired (for me 92.0 grain of N570), I still get an SD of 10-15 fps. I wouldn't dare to accept Chargemaster readings of 91.9 to 92.1, because the Chargemaster itself has an error built in. I only load readings that stay stable at 92.0 knowing that even there the real mass might be 91.5 to 92.5 grains.

If you are going out past 1500 yards where every 10fps could mean hitting or missing the target, then you want to get that charge as accurate as your eqpt will allow. If I had more patience I would weigh the cases and or sort them for volume.

 

[timelinex]

Re: 338lm Ladder results

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cali_tz</div><div class="ubbcode-body">one has to use some statistical methods to trying to quantify what are essentially random (in the statistical sense) variables. You can not conclude anything by running one of each load. You would want to run at least 5 of each load, at the same time chron each shot while shooting for ladder accuracy.

Regarding 0.1 grain differences, I have no idea what you mean by 338lm can't resolve differences of 0.1 grain, but I can say that even with measuring each load to exact 0.1 grain desired (for me 92.0 grain of N570), I still get an SD of 10-15 fps. I wouldn't dare to accept Chargemaster readings of 91.9 to 92.1, because the Chargemaster itself has an error built in. I only load readings that stay stable at 92.0 knowing that even there the real mass might be 91.5 to 92.5 grains.

If you are going out past 1500 yards where every 10fps could mean hitting or missing the target, then you want to get that charge as accurate as your eqpt will allow. If I had more patience I would weigh the cases and or sort them for volume. </div></div>

I think that what they meant by it can't resolve a .1gr difference is that nodes are much larger than that, as opposed to smaller calibers. I still weigh every single charge to exactly the same weight, atleast according to my 505 scale.

I know what your saying about statistics, I've taken an entire class on statistics. But when you start to think about statistics too hard, sometimes it over complicates very simple matters. I'm not saying that its not important to confirm results with as many rounds as you can, im saying that statistics can't always be applied as simply as many people on the forums make it out to be here. The actual chances of 5 shots or so to be very close to each other in velocity but all be anomalies is actually pretty small.


Slightly off topic, but if your interested in statistics, You will find the following interesting and it will prove how statistics isn't as straight forward as people on here make it out to be:

Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1 [but the door is not opened], and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?

The correct answer is that according to statistics it is ALWAYS beneficial to switch. Even though 'technically' each door has a 1/3 chance and it seems it wouldn't matter, it actually does according to statistics. When you choose the first door, there is a 1/3 chance your door is the prize, and a 2/3 chance that its one of the two other doors thats the prize. When he opens one of those two remaining doors, since it was a 2/3 chance it was one of those two doors, it is now a 2/3 chance it is that last remaining unopen door and still only a 1/3 chance its the door you initially chose. So that is why you switch.

Clear as mud right?