• The Shot You’ll Never Forget Giveaway - Enter To Win A Barrel From Rifle Barrel Blanks!

    Tell us about the best or most memorable shot you’ve ever taken. Contest ends June 13th and remember: subscribe for a better chance of winning!

    Join contest Subscribe

Ladder Test Question

W

Wildboarem

Private
Full Member
Minuteman
Mar 3, 2011
90
0
51
Northern CO
#1
My first question has to do with vertical dispersion. Every ladder test I've done (@300yds.)has given me some results I don't know understand. Within the string, lets say from 42gr-45gr +/-.3 will have some bullets actually drop in elevation within the ten shots. 1-3- slowly climb, 4- is down around 2, 5-7- show a node but printing higher than 1-4, 8- is back down around 3, and 9 and 10 printing back up above 5-7. I hope this is clear as mud. What I'm saying is not all the bullets print vertical always gaining in elevation, some actually drop back down the ladder even though velocity is consistently climbing. Is this normal?

Next question is during ladder test or OCW does anyone find a particular node relevant to velocity. My .260 using 3 different powders (RL-17, IMR4350, H4350) and two different 140 gr. bullets (Amax, Barnes Burner). On the 300 yd ladder there is a definite node at around 2875fps, doesn't matter which powder or bullet. I went back through some older ladder test and it is consistent. Has anyone else experienced this? Or is it coincidence?
 
#2
Re: Ladder Test Question

yes its normal for some of the faster loads to impact at the same or slightly lower on the target than slower loads. That is one of the indicators of the node.

Its easier if you post a picture of the target so folks can see exactly what you are talking about.

Jeffvn
 
#3
Re: Ladder Test Question

Is the "node" the clumping say of 3 shots and you would take the middle one to be the charge you should use, or is it the higher velocity shot of the 3 that groups lower? Getting ready to do this myself so wanting to make sure I understand it properly.
 
#4
Re: Ladder Test Question

Had the same thing happen to me after the node around the 40-41 gr mark. Target was shot @ 300. I guess the node and barrel vibration would account for the shift left as well? After the first 3 at the bottom I moved shots to center, but they gradually shifted left as they went up.



Uploaded with ImageShack.us
 
#5
Re: Ladder Test Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Heman</div><div class="ubbcode-body">Is the "node" the clumping say of 3 shots and you would take the middle one to be the charge you should use, or is it the higher velocity shot of the 3 that groups lower? Getting ready to do this myself so wanting to make sure I understand it properly. </div></div>

As with everything I think there are some different opinions. The way I've done it, I work up additional loads in .2 increments between the low and high powder charges that formed the node. At this point you know the vertical on everything should be pretty close to same (it formed a node) so I'm looking for load with best groups. I shoot 5 rounds each for this step. Once I find a couple of loads that group well within the node I'll load up 10+ of those and shoot again to verify and determine best of the two (or three) that looked good.
 
#6
Re: Ladder Test Question

The wave pattern is completely normal. What you are witnessing is teh harmonic vibrations of the barrel throwing bullets up or down (and also reight and left) depending on exactly when the bullet leaves the muzzle.

I found with 4 different 155 bullets, that they all pretty much like the same MVs (2925-2950 fps). This is in agreement with the Optimal Barrel Time theory (which is related to the Optimal Charge Weight theory).
 
#7
Re: Ladder Test Question

Something to notice in the pic that bunny posted, 39.5-42.0 were a good example of a node. Picking something in the middle to middle high on these would result in a good verticle even if your powder thrower was plus or minus .1 of a grain. Of course they should be loaded up and tested @300 to verify.
 
#8
Re: Ladder Test Question

Interesting side note here, yet related. Loads 36-37.5 actually gradually slowed down from 35.5, and started rising again after 38 (I think. Don't have my data in front of me.) And, it was consistent (within 10 fps or so) across each of the two identical ladder tests I was running at the time.

This was my first chance to use my new chronograph. I figured more powder would mean more speed....that wasn't always the case.
 
#9
Re: Ladder Test Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">The wave pattern is completely normal. What you are witnessing is teh harmonic vibrations of the barrel throwing bullets up or down (and also reight and left) depending on exactly when the bullet leaves the muzzle.

</div></div>

I would like to see you or anyone else produce documented results that remove the human factor and proves your statement to be correct.
 
#11
Re: Ladder Test Question

Animated supposition to me holds no interest.

Put a barreled action in metal fixture secured to a few tons of concrete sitting on a concrete pad, using the average barrel length and contour appropriate for the type of shooting done in this site. Test it on a wind free (or near) day outdoors, or indoors, with a chrono and strain gauge system attached to the barrel. Instrument the velocity and pressure of each shot along with plotting the POI in order on paper, preferably via a video camera down range.

There are several places that do this type of testing.

BunnyBlaster, please put a linear measuring device on your paper that you have posted up and give us what the extreme spread in inches the shots represent on paper in this fashion: Width, Height, and Total Distance between the two farthest apart shots. Thanks.
 
#12
Re: Ladder Test Question

I'll try and get something measured up this weekend. I've discarded the original target, but given that the paper sheets were standard 11 1/2" tall, I'm sure I can come up with a close measurement between shots.
 
#13
Re: Ladder Test Question

Bunnyblaster --- I'm more curious about your first 3 shots. If I understand correctly, you adjusted your elevation and/or windage after the third shot to more closely center your shots. Your 2 sighters look to be on target, only too high. The 3 shots that followed were much lower and to the right. Canting might explain this --- if you were leaning your rifle to the right, your point of impact would be low and to the right. Otherwise...????
 
#14
Re: Ladder Test Question

Cracka, I don't understand what you want answered. My question was simple, has anyone else experienced this? And some have. You haven't contributed anything to this thread, you just want to be a neigh sayer. I would like to see you lock your head in a vise, put a couple tons of concrete on top and shoot your mouth off in another thread and see if there is any vertical dispersion.
 
#15
Re: Ladder Test Question

Wildboarem --- your barrel flexes (changes shape and moves in multiple directions) every time it is fired. These barrel motions coupled with charge weights, seating depths, and pressure variations affect how well any particular barrel and load combination will shoot. That's often the reason you see charges with less powder weight impact higher on the paper than charges with higher powder weights.

The purpose of the ladder test is to find that point where the bullet leaves the barrel when it is flexing the least. The node 39.5 - 42.0 "node" in Bunnyblaster's photo illustrates what you are looking for. Not a whole lot of vertical dispersion in this node. If you load your round at the midpoint of this node, then any minor variations in charge weight should still provide consistent results.

Quite a bit has been written on this forum about barrel harmonics and there are people on this forum who have forgotten more about harmonics and internal ballistics than I will ever know. It may be worth your time to do some more research on this subject. It really helped me understand what goes on inside your barrel when you pull the trigger.

Bob
 
#17
Re: Ladder Test Question

Thanks Nut, I don't know everything and your explanation is a little different and helps me to wrap my head around it. One would think that if you were to be consistent the bullet would exit the barrel the same every time. But I guess as slow as the bullet is leaving the barrel in comparison to how fast the vibrations are moving one would want as many vibrations away from the muzzle as possible when the bullet is exiting (node vs. scatter node?).
 
#18
Re: Ladder Test Question

Wildboarem --- that's where bullet seating depth becomes important, because it is a determinant of how long the bullet stays in the barrel. Whether you ladder test or use the OCW method, once you find your optimal charge weight, the next step is varying the seating depth of your loads and see how well they group. Hopefully, at the end, you will have a charge weight and seating depth that permit your load to consistently leave the barrel when it is flexing the least. That should give you an accurate load. It works for me.
Bob
 
#19
Re: Ladder Test Question

Squarenut - the two sighter shots were a normal load I had for this gun (41gr IMR 4064, 175 SMK). After confirming those, I adjusted down (only elevation. The next three shots were way under powered, and threw right. There were differences in the load make up besides powder between my ladder loads, and my shells already loaded. The rounds I used for sighting had a Remington Nickel brass case and used a Winchester Primer. The ladder rounds had a Nosler case and CCI Primers, and they were seated slightly longer. My guess was this changed the barrel harmonic and resulted in a impact to the right. Could be wrong, just a guess.

When I noticed the rounds to the right, I adjusted only the windage to the left. From that point, I never made any other adjustments.

I can't verify that I wasn't canting the rifle slightly. Could have happened.
 
#21
Re: Ladder Test Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H_Cracka</div><div class="ubbcode-body">Animated supposition to me holds no interest.

Put a barreled action in metal fixture secured to a few tons of concrete sitting on a concrete pad, using the average barrel length and contour appropriate for the type of shooting done in this site. Test it on a wind free (or near) day outdoors, or indoors, with a chrono and strain gauge system attached to the barrel. Instrument the velocity and pressure of each shot along with plotting the POI in order on paper, preferably via a video camera down range.

There are several places that do this type of testing.

BunnyBlaster, please put a linear measuring device on your paper that you have posted up and give us what the extreme spread in inches the shots represent on paper in this fashion: Width, Height, and Total Distance between the two farthest apart shots. Thanks. </div></div>

So what are you saying here?
You have never seen a barrel track left to right in a ladder test?
Just curious.
 
#22
Re: Ladder Test Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wildboarem</div><div class="ubbcode-body">Cracka, I don't understand what you want answered. My question was simple, has anyone else experienced this? And some have. You haven't contributed anything to this thread, you just want to be a neigh sayer. I would like to see you lock your head in a vise, put a couple tons of concrete on top and shoot your mouth off in another thread and see if there is any vertical dispersion. </div></div>

Yes people experience it often - the actual cause of the dispursion is what I am addressing, not what shows up on paper.
 
You must log in or register to reply here.

Similar threads

W
Interpreting Ladder Test
Replies
13
Views
539
MarkyMark007
MarkyMark007
Shayne Ward
Sierra 110 in a Dasher Questions
Replies
2
Views
194
LR1845
L
Rommel Garcia
How To Read OCW Test Results
Replies
17
Views
706
Csafisher
C
N
First Timer Help! LR Hunting 308 Handloads
Replies
44
Views
2K
JerkyFreak
JerkyFreak
Jayjay1
Almost new rifle - groups spread horizontal
Replies
38
Views
1K
bax
B
Top Bottom
Back
Home
Forums
Merch
Alerts