Where are the nodes? Data included..

[Dthomas3523]

I've always did my test the way I described. For me, more powder does not mean more speed in my case and the tests I've done using a Magneto V3. Here are the numbers from my last test.

42.3 - 2667
42.5 - 2662
42.7 - 2676
42.9 - 2667
43.1 - 2707
43.3 - 2703
43.5 - 2731
43.7 - 2744
43.9 - 2756
44.1 - 2762
44.3 - 2784
44.5 - 2784

I tested loads at both 43.2 and 44.4, settling on the 44.4 following seating depth test. Again, this is how I've always done my loads and I've never any issues. Now I'm sure there are better ways of doing things, and I'll admit, I'm not looking for BR accuracy as I shoot mainly steel. The above process works for me. That's why I stick with it. I don't really pay attention to the powder charge, but mainly the bullet speed. Only thing I'm concerned about on powder charge is over charging, and the casing will tell me that. I'm sure there is another node above the 44.5, but that's as fast as I wanted to run the 175SMK.

After settling on a load, it averaged out at 2768 across six shots. I took the data I got from the chrono to a distance of 804 to true MV and it ended up being 2764 once that was completed.

Shoot 20 or 30 rounds of each and take the average velocity.

If you can do that, and then repeat it several times, while showing more powder = same speed….there’s probably a list of people at MIT who would be interested in talking to you (just making joke to make a point).

Velocity “flat spots” are nothing more than the ES of small sample sizes overlapping when one round shoots on the high end of the ES and the other round shoots on the low end of ES.

The reason it “works” for shooting steel and prs type stuff is because for the most part, you can load any random charge weight, tune seating depth, and go win a prs match.

 

[jelenko]

Velocity “flat spots” are nothing more than the ES of small sample sizes overlapping when one round shoots on the high end of the ES and the other round shoots on the low end of ES.

This!!

 

[dcali]

I would seek a friend with an eTarget like a ShotMarker and beg for a day at 600 yards or more. The eTarget makes collecting the groups or verticals much easier.

Just quoting for emphasis. Shotmarkers make ladder tests painfully simple. Just record the velocity of each shot (with a lab radar, not the shot marker), and let the shot market record the vertical position. No messing with magic markers or wondering which hole belongs to which bullet.

 

[Ledd Slinger]

Colored bullets work but aren’t the easiest to distinguish. I just use my spotting scope to map the impacts on a piece of notepaper like they do in the pits at a match. No trouble seeing holes at 870 yards with my spotting scope in the morning before mirage gets bad. Would really like to try a Shotmarker some day, but we don’t have any actual long range shooting ranges around here. All long range shooting is done on public lands up in the mountains.

 

[Webster]

I was running a ladder a couple weeks ago and when the rifle was transitioning from a lower node to an upper node (based on POI on target) I had a big velocity spread on the transitional charge weight between the two nodes. The upper speed bullet on the spread of the transition weight was the same as others in the upper node and hit in the same spot vertically as the rest of the bullets in the upper node. the lower speed round was much closer to the speeds of the lower node and hit in line vertically with those rounds. All shot at 870 yards. The next charge weights up to max pressure stayed in the upper node impact zone.

Had I just been firing at 100 yards and just recording speeds, I would have had no clue what to expect from that speed spread in that charge weight an in no way know what was going on. But seeing the impacts on paper at long range (and talking to a friend of mine that is a very accomplished 1K BR shooter), it helped me understand what was happening. All the other charge weights in the lower and upper nodes only had an ES of less than 10 fps. So I only saw the big spread when the rifle was transitioning nodes. Total speed difference between the lower and upper node was about 60-70 fps.

Now switch to one of my different rifles in a different caliber using different bullets, powder, and primers, I’ve run ladder tests where you could stack three 3 shot groups (9 rounds) on top of each other with a charge weight spread of 1.5gr and a velocity spread of 60-80 fps. Go figure...

So as we both agree, reading speed alone doesn’t really tell us anything. Shooting paper and analyzing point of impact of bullets is the only way to know what’s going on and what the rifle likes.

Plotting speed and looking for flat spots is ignoring the ES. I just look at the target. Looking for flat spots in fps ignores the vibration pattern of the barrel.