Home Forums Reloading Big Game Rifles Can Someone Please Explain Ladder, Accuracy Node, etc?

After 40 years of loading, it seems there is more to learn. Could the kind folks here explain how to formulate a ladder (and what it's supposed to do for you) and how to find an accuracy node, if that's the right term?

ALso, does any of this matter in sporter weight rifles?

I may already be doing both, without knowing what they're called.

Thanks
Pete

The ladder method is a means of adjusting your load so that the bullet exits the barrel at the right time to minimize the effect of barrel whip. The node is the point at which the barrel is nearly standing still. Actually, for a small instant, it does stand still, but there is a region around that point where it isn't moving much. When bullets exit near the node they tend to group well, and the POI is relatively insensitive to small changes in charge.

There are some complicated explanations of what a node is. This is probably an over simplification, and goes along the same line as denton explained.

Consider the barrel as vibrating up and down, with 12:00 at the top, 3:00 on the way down, but straight, 6:00 at full down, and 9:00 as straight but on the way up.

Next consider that fast bullets exit the muzzle sooner than slow ones. And, the barrel is really only stopped at the top and bottom of the vibration cycle.

Lets consider each one:

12:00 - If a fast bullet exits at say 11:00 (not all the way up), and a slow bullet exits at 12:00, then you get a compensating effect. But this may be an edge of the cliff node. If the slow bullet exits at 1:00 and the fast at 12:00. then you get the reverse effect. So there is an anti-node right after 12:00.

3:00 - The barrel is at maximum speed and fast bullets will always be higher than slow, and this is bad. A real anti-node spot.

6:00 - The fast bullets exiting at 5:00 will be higher than slow at 6:00, so an anti-node. Then you get a good node between 6:00 and 7:00, potentially as good as the 11:00 to 12:00 node.

9:00 - Barrel at max speed again, but fast bullets exit low, and slow ones higher. May be volatile, but at least it is in the right direction.

I think it is real. You can control which node by adjusting muzzle velocity. You can see it the most at longer distances. Here is the results of a ladder test I did at 300 meters last week. You can see where velocity goes up but POI elevation is flat or even goes down. Even with different bullets it can happen at the same velocity, because velocity determines when the bullet gets to the muzzle.



There is a lot of info out there on the method. But this is probably one of the better ones.

Incremental Load Development

Is it necessary for a hunting gun? Probably not! It will not make a silk purse out of a sows ear.

I don't know about the necessity but the ladder method will certainly speed up finding the "sweet spot" aka node with a certain powder. bullet, etc combo.
Determine your choice of bullets, powder. primer, etc. I start my powder charge at about 70-75% of book max. (I've already determined that I can go to max but that's another story) Load one cartridge up with your starting powder charge. Then load another exactly the same except your powder charge is 1-3grs higher.(for a small case, you might want to move up in smaller amounts)Continue loading adding powder per cartridge until you're at max.
To take real advantage of the ladder you need to have your target at least 200 yards away. Begin your shooting on a calm day and shoot each bullet at the same bullseye on the target. Plot each bullet strike on a dope sheet.
When you bring your target in, you will notice that the bullets are scattered around on the target but some shots are clustered much closer than others. You may have two of these clusters. The clusters are your accuracy nodes and within the powder range of those shots is where you will find your best accuracy. Now it's time to load up groups of three cartridges within that powder range using smaller units of increase. Once you've determined the best accuracy, it doesn't hurt to try a couple groups that's a quarter grain above and below. You want to center the node as nearly as possible in case --as posted above-- you have a bullet leave at 11o'clock or 1o'clock.
Once you have your basic load, you can jim around with different COLs, primers, and such.
The problem with this method is not everybody has a 200+ yard range and a spotting scope capable of seeing bullet holes at the distance.
It doesn't seem to work at short range --100 yards-- because the bullets strike too close to determine the clusters.

Thanks guys, I get it now.
THough as I suspected, this method really has no application in a 6.5 lb 308 or similar 350 yard deer rifle.

Pete

Pete, if your rifle will group in the 0.5" range, then it can work, and can help gain you some consistency in the groups. If your hunter is spraying them into 3" groups like some of mine do, then it is an exercise in frustration.

To some degree the method works better on a skinny hunting barrel than a thick target barrel. The skinny barrel vibrates up and down more, so there is more of an effect in getting the sweet spot.

Some of course really only want maximum load so, just load up until they see signs of pressure and back off a bit.

The "ladder method" and "nodes." I don't often write this much but it's raining outside.

Lets make it simple... and understand that the process fully applies to any rifle.

First, the ladder is mostly a way to quickly find charges ranges worth more pursuit. Meaning it's basically a fast process to eliminate poor loads rather than an instant way to pin point the "best" load. The idea is to quickly find an accuracy node, or range, for both powder charge weight and seating/OAL. In application the process shows that the best values for an accurate load are a window, not a specific spot +/- nothing. Identifying and then loading inside the node/window ranges produces ammo that isn't twitchy to tiny loading variations.

Starting with a new bullet and powder, load a "ladder" of slowly increasing rounds moving up from the book start load to as far as you want to go. (I number each round with a Sharpe pen so they can't get mixed up if I drop 'em!) Depending on case size, load in carefully weighed steps from .2 gr. to no more than .5 gr. per step. If you make the "ladder" steps too large you can easily go right over a node! Seat bullets so they're off the lands maybe 20-30 thou to start.

Fire each round very carefully and allow the barrel to cool between shots or heat warping and bad shooting will destroy any results you may find.

Either go down range and number each hole as you fire it or use a spotting scope to make a record, either way you MUST keep accurate track of every hole or you negate your results.

I have to do my ladder testing at 100 yards. I keep track of each shot by shooting each numbered round at one numbered target. When I'm finished I stack each target on top of a blank target, carefully marking and numbering each hole's location, to make a "composite" of the string. Carefully examine the completed composite target; look for three consectutive holes that are quite close together. That kind of grouping suggests an accuracy node and the end of the first phase.


[It's not officially a part of the Laddder method but, as a safety/info matter, I like to record and graph the velocity of each step as I shoot. The graph lets me see how the charges vs. velocity progresses. The graph won't be linear, it will occasionally even move backwards, but one sign of excessive pressure is a speed plateau as charges/pressures increase. IF I find the speed stays about the same for maybe three-four small consecutive charges I stop no matter the lack of other signs of pressure. So far, so good...I find good loads and nothing has blown up on me yet!]


Now, load more ammo. This time try groups of 3 to 5 rounds in .1 gr. steps centered on the middle load of your apperant node. That should let you find the full charge window of what your rig likes with that bullet and powder AND show you how much charge variation it takes to make a difference in accuracy. (I often find windows as wide as .5 gr., sometimes more.)

Then, using your newly established charge, do a third ladder working on the seating by moving maybe 5 thou steps both ways from your initial OAL. Move longer to maybe .005" off the lands and shorter to as much as .100", or more, off. Again, make and examine a composite target to find the best seaing window.

Load in the middle of the best charge and seating nodes and you should be done.

Developing loads the ladder way saves a LOT of time and components compared to the old way of making each small change/seating step in groups of 5 rounds!

KY, thanks, those 2 sights didn't appear when I googled the subject.

Boom, I also use a chrono whenever I'm working in unknown load territory. That flattening of the vel/charge curve has saved my butt more than once.

Ron, I'll have to play with this when time allows. The gunroom has a few occupants that might qualify.

Another question, how does one choose a powder to start with? The average of several manuals giving the most accurate powder in a given ctg?

Pete

Powder selection: If I check more than one manual it's only to see what produces the highest velocity (prediction) for the bullet weight I wish to shoot.

I chose my cartridges for their performance and I don't load them down. If I can't find an accuracy node at or very near max book velocity I try another powder, usually one a step or so faster burning.

I'm a Florida boy (Jax) but don't know where Viagra Falls is. Maybe on headwaters of the Limpstick River?

Easily amongst the most fruitless of ways to spend primers................

A ladder is what you use to get up on ther roof. An accuracy node is kinda like a lymph node, only it releases accuracy instead of lymph.

A lotta folks who can't shoot well are plagued with underactive accuracy nodes.........grin.

I'm floored that guys believe this schitt?!!?

Don't anyone shoot anymore? WTF?....................

I think it is all about velocity. Your barrel vibration is pretty much fixed by the weight, length, and profile. So all you are doing is changing the time the bullet arrives at the muzzle by adjusting velocity. A good velocity in one bullet is likely to be good in another. You pretty much have to test over a wide range to identify the velocity sweet spots. Most do it with a course load adjustment first -- about 1 to 1.5% powder weight steps. Then when you find an interesting spot, you reduce that. The graph I posted earlier was a second refinement of an area of interest.

Different religion I suppose. Just reading the procedure makes my head hurt.

I like to moly up, kiss lands (when practical), find pressure, and back off a couple grains with the 308, and 30-06 case. So far, so good.

The problem is that it doesn't take as much temperature difference as you might think to equal half a grain or a grain of powder. If you do find the sweet spot, it had better be a pretty broad sweet spot.

It helps to use the temperature insensitive powders like Hodgdon Extreme.

Pete,

Ladders: sometimes they work, sometimes they don't. IMHO, the more inherently accurate the rifle (not the load) the better it works. Here are some ladders I shot a number of years back with a pencil thin barreled 30-06AI.




The second ladder proved to provide my favorite load.

Here are some ladders I shot just a few days back with a 6.5x47 Lapua in a very well put together rifle built by Chris Matthews of http://longshotriflesllc.com/

140 Accubond with Rel 17.

140 Berger VLD with Rel 17.


The majority of ladders I've seen climb up and to the right. When I see a ladder like this last one, I get very excited. It means the node is quite large and the barrel harmonics are very still; IMHO.

Alan

http://www.the-long-family.com/OBT_paper.htm

IMO, there is absolutely no reason to shoot all the shots required in a Audette ladder. Just calculate the node you want, verify on the range, and you are done.

Stick is right. This stuff REALLY cuts down on your shooting time. HTH, Dutch.

Interesting article. For sure if you can accurately calculate barrel time, and know what a good barrel time for your barrel is, then you can cut to the chase much quicker. Another close substitute is velocity. Not sure I believe the author's thinking on what causes nodes though. Varmint Al's explanation seems more plausible.