Ladder test interpretations please!

[jdbell2004]

Hi all! I performed a couple ladder tests over the past few weeks. I'm shooting a Howa .308 with a 20" bull barrel in a B&C Medalist stock with a 4-16x Monarch. I was only able to shoot just over 350 yards. The flowing picture is of my refined test of .3gr instruments. I was shooting prone off a sandbag.

I read the sticky post about doing the ladder test but did not remember reading anything about whether or not to let the barrel cool between shots. Mine never got too hot to touch but I only allowed about a minute and a half between shots. At one point I waited several minutes as someone drove out to where we were shooting. Should I have let it fully cool between shots or not? I ask because some of my hotter loads hit below the cooler ones. I was very consistent with my case prep.

Any input is greatly appreciated!

 

[tullius]

Re: Ladder test interpretations please!

Before running more ladder tests, you need to work on the fundamentals of marksmanship. Rebuild your position, check NPA, proper cheek weld, good sight picture/clear field of view, smooth trigger manipulation. You must be able to achieve a near perfect break on all shots fired in a ladder test to be able accurately interpret the data.

Barring something drastically wrong with the rifle, ammunition, or environs (and that's almost definitively not the case here because you're hitting the paper), physics has no explanation for the faster loads striking significantly lower than the slower loads save shooter error.

I have had to abandon a few ladder tests because I wasn't shooting well enough that particular day to glean anything from running the test, spend the remainder of the time working on fundamentals, and run the tests another day (successfully).

 

[jdbell2004]

Re: Ladder test interpretations please!

I'm fairly confident in my shooting skill. I have 8 years firing the m16 with the Army and about 6 with bolt actions. I can shoot tight groups and have from a bench with a bag.

I will admit, shooting that ladder test in the prone was less than comfortable. I did have trouble keeping butt placement on my shoulder consistent but I figured since I had no scope shadow I was good to go. Maybe I need to spend more time getting comfortable before the trigger is pulled each session.

 

[tullius]

Re: Ladder test interpretations please!

Few other things:

-Barrel cooling/resting is a chimera here.

-Did you find the max load for your rifle? Don't know what powder, case, bullet, primer and chamber you're using, but the loads look on the light side, but maybe not. Guessing you found max load on your primary go-round.

-A more uniform aiming point on the target might help consistency, I trace the outline of a Copenhagen can and color inside the lines.


Oh, fill out your profile before BOLTRIPPER latches onto you..

 

[jdbell2004]

Re: Ladder test interpretations please!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tullius</div><div class="ubbcode-body">Few other things:

-Barrel cooling/resting is a chimera here.
..

</div></div>

Explain chimera...

I went one grain over book max in my initial ladder test. No signs of over pressure. I could have gone higher but powder isn't free. I pinch pennys like they're in short supply. There really has to be a significant consistency gain for me to bring it up a grain or two.

I'll run another test starting just below the high charge of my first test to a few grains above book max then run a refined test off of that. I'll spend some extra time getting into a consistent comfortable position before firing.

Cool the barrel or no?

 

[parker_chp]

Re: Ladder test interpretations please!

The first ladder I ran with 175smks was with varget 42-45gr half gr incraments @450 yards.I ended up with a 6 (2-7) shot group that was 1.5in high and 1.3in wide.#1 was 3in low. I just packed my bags and went home. I never understood it or repeated it. But I ran .2gr incraments(43.8-45) 3 shot ea. and they all over lapped.I just shoot the tightest vertical.

 

[parker_chp]

Re: Ladder test interpretations please!

The first ladder I ran with 175smks was with varget 42-45gr half gr incraments @450 yards.I ended up with a 6 (2-7) shot group that was 1.5in high and 1.3in wide.#1 was 3in low. I just packed my bags and went home. I never understood it or repeated it. But I ran .2gr incraments(43.8-45) 3 shot ea. and they all over lapped.I just shoot the tightest vertical.

 

[gcoulsey]

Re: Ladder test interpretations please!

Faster loads can (and very often do) strike lower on such tests,
It all depends on at what point in the barrels 'whip' the bullet exits the muzzle..
The faster bullet can exit sooner as the barrel is flexing upwards, giving lower strikes on paper, also the faster bullet has less time to be affected by muzzle rise induced by recoil etc, blah blah blah..

So sometimes, it happens!
If you find yourself struggling with ladder tests, read up about OCW tests,
You might get on a bit better with them,
Good luck!

 

[tullius]

Re: Ladder test interpretations please!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: PORK</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tullius</div><div class="ubbcode-body">Few other things:

-Barrel cooling/resting is a chimera here.
..

</div></div>

Explain chimera...

I went one grain over book max in my initial ladder test. No signs of over pressure. I could have gone higher but powder isn't free. I pinch pennys like they're in short supply. There really has to be a significant consistency gain for me to bring it up a grain or two.

I'll run another test starting just below the high charge of my first test to a few grains above book max then run a refined test off of that. I'll spend some extra time getting into a consistent comfortable position before firing.

Cool the barrel or no?
</div></div>

<span style="font-weight: bold">chimera /kVI"mI@r@, kI-/ (also chimaera)
· n.
1 Greek Mythology a fire-breathing female monster with a lion’s head, a goat’s body, and a serpent’s tail.
<span style="color: #000099">2 something hoped for but illusory or impossible to achieve.</span>
3 Biology an organism containing a mixture of genetically different tissues, formed by processes such as fusion of early embryos, grafting, or mutation.
4 (chimaera) a long-tailed cartilaginous marine fish with an erect spine before the first dorsal fin. [Chimaera and other genera, family Chimaeridae.]
– DERIVATIVES chimeric /-"mErIk/ adj. chimerical adj. chimerically adv.
– ORIGIN ME: via L. from Gk khimaira ‘she-goat or chimera’.</span>


You're on the right track to go higher on the charge until you determine the max. load for your rifle. Most of my rifles shoot best on the hot end (watch for pressure signs very carefully). Plus you'll have the advantage of the bullet spending less time in the air and giving the wind less time to act on it. Two or three grains extra powder doesn't really cost that much, especially when you're just ladder testing: you can bump down to the next node later if needed.

Don't worry about the temperature of the barrel, build a good consistent prone position and get a perfect break on every shot. You'll get it.