Ladder Test means WHAT?

[punkwood2k]

I'm running my first two ladder tests this weekend. One on a new bullet I've never developed before, and another test on one I already refined but I want to see if it jives with what I already developed..

Now, my question is, what exactly is the Ladder test testing? I understand the Sine wave theory, and bullet exiting the barrel at its point of least motion, and all that. Is it testing the muzzle velocity of the bullet? I'm asking because if I want to further tweak the bullet after finding my node point, it would involve tweaking the charge a bit, or the seating depth and thus pressure / MV would change.. So as long as I adjust the variables so that the muzzle velocity is the same no matter what, the bullet should ALWAYS exit at that node point? Meaning I can do whatever I want to that bullet, as long as the velocity stays the same?

 

[rjacobs]

Somebody will come along with way more knowledge than me and I dont do ladder tests.

From what I understand with the ladder you are looking for the most common bullet impacts so say a group of 3 or 4 loads that all have relatively the same POI.

THEN you can take those 3 or 4 loads and further develop them by working around them in .1g differences as well as playing with seating depth to find the magic combination.

I much prefer OCW as you dont need a 500+ yard range to do them. I also am stuck loading to mag length in all my guns so I cant play with seating depth much(except to add MORE jump). OCW gets ME to the end point much quicker than I imagine running a ladder would get me.

 

[Darkside-Six]

This is what I did when I developed my load.

Took the OCW and started at the low end and increased my loads by .5 grains per round from low to high. (42, 42.5, 43, 43.5....and so on)
Then I fired each round at the same target starting with the lowest and progressed up.

I then looked at what was my best grouping.....say 43, 43.5, and 44 all had a nice group together.

I then went back and made 5 rounds of each of those loads, then fired each group at separate targets and looked for the best 5 round group.

That got me right where I needed to go. I guess if I wanted to really fine tune it I could have went back to those 3 loads and increased by .2 grains but I ended up with a spot on load so I was good.

Hope that makes sense.

 

[Bill Larson]

it will idenify a sweet AREA.....that deserves careful look.....

 

[Thumper580]

Look for,the smallest group in the test. Load that group up again, vary the seating depth at that charge weight. Maybe start at the lands then back the bullet off 5,10,15,20,25 thousandths. Somewhere in that range the groups will get better or worse. The smallest group indicates the proper seating depth at that charge weight. Basically, the final fine tuning of your load. Good luck.

 

[jdonovan]

Is it testing the muzzle velocity of the bullet?

Its testing the position of the barrel within the sine wave. Which I'll assume to be more a measure of projectile in barrel time. This in barrel time probably correlates strongly to velocity, but not 100% as different powders/charges may achieve the same velocity, but may cause enough of a in-barrel time to move you out of the sweet spot of a node.

The other theory on the identification of a 'node', is that there is some room on either side of the node to be close enough to a stationary point in the sine wave that the POI is not disturbed by slight changes in the time of exit from the barrel.

I would operate under the theory that velocity is the indicator of the node for purposes of load work up. Once you identify a OAL you like, you may want to re-do the OCW test around that OAL to make sure you are not on the edge of a node, vs more centered within the node.