Help interpreting Ladder Test results

[petenz]

I did my first ladder test ever today


Rifle is a remington 700 SPS stainless, .270Win glass bedded in a laminate stock with the trigger lightened. I got the smith to check the crown and he said it was fine although the bore is machined very roughly. Will be rebarreling eventually.

I was shooting 130gr NBT's, started at 53.gr of ADI AR2209 and went up to 57 gr, was planning on stopping when I hit pressure signs as ADI max is 55gr of 2209, but got no signs of high pressure at all... projectiles were seated out as far as possible while still fitting the mag, temp was 31'C (87F).

Range was 220m (240 yards).
No|Charge|Vel.
1: 53.6gr : 3034
2: 53.8gr : 3046
3: 54gr : chrono didn't read it
4: 54.2gr : 3066
5: 54.4gr : 3067
6: 54.6gr : 3069
7: 54.8gr : 3088
8: 55gr : 3082
9: 55.2gr : 3095
10: 55.4gr : 3139
11: 55.6gr : 3134
12: 55.8gr : 3167
13: 56gr : 3241 <-- seems too fast - chrono error?
14: 56.2gr : chrono didn't read it
15: 56.4gr : 3162
16: 56.6gr : 3110
17: 56.8gr : 3205
18: 57gr : 3168

What should I work on? I was thinking something around the 15, 16, 17 might be worth a second look, velocities are inconsistent but I think the chrony was a bit dodgy, it failed to read twice...

Or my brass might just be inconsistent, it's Federal stuff, the 140gr accubond load on that target shot 2 .5" groups at 115m (125 yards) the other day, today (same temp etc) it shot that 4" group at 220 Going to weigh the brass and toss any fliers. Need to have a load sorted by this weekend so no time to get new brass

 

[petenz]

anyone?

 

[AJ Peacock]

How much wind was there when you did the test?

When the wind is blowing at all, I only take into consideration the vertical distribution on my ladder tests (I know there is always a vertical component to the wind, but I don't run a ladder when the wind is blowing very hard).

I'd look at the area around shot 15-17 as you noted and see what was up with the velocity readings. Depending on what you are looking for, I'd also look at shots 1-4.

AJ

 

[petenz]

I am now a convert to the way of the ladder test.


Shot at 100 metres, 3184 FPS average velocity, about a 10-15 standard deviation (haven't worked that out properly yet), .5MOA

 

[royinidaho]

You done good.

You have a real decent load worked up and only used 24 shots not counting the 140s.

About 12 more shots to get the drop chart out to at least 800 meters and your set to go. I'd recommend two shots at each distance unless the two shots get flaky. And you are ready to do some harvesting.

You gotta love the 270 WIN and your velocities are are precisely where they should be for that bullet.

Could you ship me some of that powder.

 

[petenz]

I think H4350 is the exact same powder, if I recall correctly ADI make it for them and it's repackaged.... This is an over max load but I am getting no pressure signs at all...

Should work well for hunting until I get the 140gr accubonds sorted...

 

[petenz]

Sd = 7.2

Es = 18

 

[Weda]

Look at your 15,16,17 shots and where they printed....

15: 56.4gr : 3162
16: 56.6gr : 3110
17: 56.8gr : 3205

In therory I would work with the #16 load.. why

because if you are off by 1 or 2 grs, in theroy, your rifle will print them in the same place or nearly the same.

You could always do this..

fire 2 rounds to remeove Cold bore variable.

load 3 rounds of the 15, 16 and 17 loads

fire #1-15, 16, 17, #2-15, 16, 17, 3#-15, 16, 17

fire each shot after a 1 or 2 min barrel cooling period between each 15,16,17

keeping all three 15's at the same POA, all 16's at the same POA and all 17's at the same POA. Now lay the 3 groups on top of each other or compare. see what ya got.

 

[petenz]

L
In therory I would work with the #16 load.. why

because if you are off by 1 or 2 grs, in theroy, your rifle will print them in the same place or nearly the same.

I tried loads 15 16 17 yesterday, 15 shot well, 16 shot like ****, 1.5" groups, 17 shot ok

I am going to try 15 again, it put 2 through the same hole and one about 1" away but that was from a clean, cold barrel.....

Yeah I forgot to fire foulers

 

[squirrelduster]

If you continue to see the group size change radically then settle down again, pull your scope and mounts off and remount the bases with loctite.
I have spent a lot of time chasing my tail when it was mounts and bases. I had a set of Leupold rings shear off so I purchased a set of Warne rings and bases for my 300. No problems since.