Dasher RS52 Ladder test result

[macdeerhunter]

Here is result from my Ladder testing early today. I would appreciate help from other members about interpretation, specially about velocity assessment (I read DMoran posts about that). Here is details:

Rifle: custom built on Mini Mauser action, LWalther barrel 21" long, 1:8" twist, .272" neck, .080" freebore length (short because of magazine feeding on 2.350"), 4-16x50 Vortex PST FFP scope, Harris 9-13 bipod. Stock is similar in outer shape to AI L96A1. Weight is 4.9kg with scope.

Ammo: 6mm Dasher, Norma 6 BR cases neck sorted to .0015", ReloadSwiss RS52 powder 29.3 to 32gr, #450 primer and 105gr Nosler CC bullets, -.010 from the lands.

Range condition: Distance 500m ( aprx 550 yards), 25 C (77F), 924mbar (27.3 in/Hg), 50% H, variable wind up to 5 mph.

I loaded 10 rounds with 0.3gr increment, starting from 29.3 to 32gr. I started from the lightest load and go up to the heaviest, before that I shot few bullets to sight in. I also shot another lightest one at the end (because I warm barrel with shooting (I know that this is not smart but I was in hurry) so I wanted to see how much my velocity changed from the same load fired at the beginning of the test).

Result can be seen on attached photo. For better view I will write list here in order how I shot (charge of powder, speed 10m from hrono, vertical distance from bottom line):
1. 29.3gr - 2654 fps - 2"
2. 29.6gr - 2680 fps - 4.7"
3. 29.9gr - 2703 fps - 9.25"
4. 30.2gr - 2720 fps - 8.2"
5. 30.5gr - 2767 fps - 8.25"
6. 30.8gr - 2773 fps - 8.85"
7. 31.1gr - 2795 fps - 10.7"
8. 31.4gr - 2841 fps - 15" (felt on bolt opening)
9. 31.7gr - 2865 fps - 15.75" (hard on bolt)
10. 32gr - 2892 fps - 16.5" (hard on bolt)
11. 29.3gr - 2693 fps - 5.4" (warm barrel, compared from the same charge in first shot).

Please could you help me with assessment of vertical POI movement, specially velocities, give me your opinion, advice... witch load to choose.


Here is my rifle...

... and shooting range.

 

[dmoran]

^^^^ I agree with @tom 's assessment

 

[macdeerhunter]

Thank you both for the answers and help.
In meantime I conducted another Ladder test with the same component, range ... etc, just this time I shot 3 round and let barrel to cool down for 10 min. Range condition was the same, early morning but ... it's too hot under sun again, even with one round you can felt with hand that barrel is heated by little. Even so... I not allowed barrel to be warm as yesterday in the last rounds. Also, I need to note that this time I shot charges randomly, not in order from lightest to heaviest like in previous test.

Here is result from lowest to heaviest, not in order how was shot, also right is velocity from yesterday from the same load:

1. 29.3gr - 2657 fps - 0" / 2654 fps
2. 29.6gr - 2706 fps - 3.9" / 2680 fps
3. 29.9gr - 2726 fps - 4.5" / 2703 fps
4. 30.2gr - 2740 fps - 3.6" / 2720 fps
5. 30.5gr - 2750 fps - 7.5" / 2767 fps
6. 30.8gr - 2793 fps - 10.2" / 2773 fps
7. 31.1gr - 2812 fps - 10" / 2795 fps
8. 31.4gr - 2832 fps - 8.9" / 2841 fps
9. 31.7gr - 2851 fps - 13.2" (felt on bolt opening) / 2865 fps
10. 32gr - 2858 fps - 14.9" (hard on bolt) / 2892 fps

I measured vertical height by my 3 control shots (31gr RS52) so it can be roughly comparable to previous target from yesterday (starting horizontal line is on the aprx same distance from 3 control 31gr shots fired from yesterday too).

Please can you give me assessment now, what can be concluded from this results?

 

[macdeerhunter]

Thank you for advice. Mine platform shot first couple of rounds in the same way as it warm up, but I don't know how it reflected here... I will try to fine tune 29.9-30.2 as per your advice at 1000 and will post result.
I used Alpha Shooting Chrony with set diffusers, 12m from the muzzle. I can't say that I mounted it perfectly in the same way from previous test because of terrain configuration but it was close (if this affects that much on read velocity?).

Regarding RS52 powder, I actually don't know much about the behavior of this powder, I noted only that is temperature sensitive because I got minimum 50fps higher velocities from 70F to 100F some time when I tried and velocity started to increase as I shot. I bought it as replacement for Varget which become hardly available in Europe. It is high energy, Swiss made, the same line of powder like RL17 which we call here RS60 (Laurie explained that in detail in my previous thread regarding RS52 powder), I can say identically formulated, just faster, similar to Varget burning rate. Maybe this reflect on results too?

I found written data from 15 days ago when I shot first 5 rounds to try this new powder, with the same case/primer/bullet, 31.5gr (31.4gr in the ladder tests give me avg of 2836fps now) in temperature of 100F, you can see interesting increasing with every round (barrel is so warm as well as ammo), I got 1. 2883, 2. 2893, 3. 2916, 4. 2945, 5. 2962fps and group from the picture (0.5MOA whole, with first 4 bullets much much less). You can notice 47fps initial increasing of velocity with first round and velocity started to go up with every fired round, finished with fifth as far as 126fps more than nearly the same amount of powder fired in the both Ladder tests described above on aprx 77F. So...?