ladder test - is it good only for that bullet and powder?

[alanw]

I will ladder test my new Krieger/Hall 6.5x284 with 140 Berger Hybrids, starting with 7828. If a node comes in around 2950, let's say, does that mean that regardless of powder chosen, that the 140 Hybrid will like the 2950 velocity?
Does it apply to other 140 - 142 gr bullets, or do I have to ladder test any change from the 140 Hybrids/7828?
Thanks very much for any replies.
Alan

 

[BoydAllen]

Perhaps you may have overlooked that different seating depths, and neck tensions, even at the same velocity, may yield different results, and different bullets may have different requirements for these variables. That velocity "nodes" exist does not negate these other factors. I have not determined this to be true with the caliber and bullets that you are asking about, but have found it to be true with others.

 

[alanw]

So I should do seating depth tests first, it sounds like? It also seems that a velocity node will only be good for that bullet.

 

[jbpmidas]

I always retest any changes, powder, bullet, primer, case, etc... HAving said that, I've never used a combination that gives the short barrel life like the 6.5-284.

 

[XTR]

The node is good for that bullet, and you want to find the node before you play with seating depth.

For a given bullet it seams that the nodes do show some consistency from rifle to rifle. Most people shooting 308s with 175 SMKs or 185 Bergers over Varget in WW brass find a node at about 44.0 to 44.5 grains. It seems to be there for most people, so if you have a bullet/brass/powder combo that others are using you may be able to take something away from what they have learned.

Ultimate velocity will depend on too many things. Finding the node is about finding the powder charge that works for your gun. Getting Chrono data at the same time is helpful in that you don't need to shoot again to get the info or if you are trying to get to a certain velocity for something like 1000 yd shooting.

Look up OCW testing.

 

[alanw]

The OCW is quite interesting. Thanks. I'll also give it a try.

 

[Keith Glasscock]

Is the node velocity the same with different powders?

I used to think that it was. That is until I gave her a go. While some powders do node up at similar velocities and seating depths, others do not. I have found that Chris Long has something with his OBT theory, but I think his node list is incomplete, per se.

I have found great loads between Chris' nodes, and never understood why. The really baffling thing I've found is that I can run two different powders at different velocities, but the same barrel time and get good results out of each (assuming everything else is held constant).

While predicting a good load with QL just isn't going to happen unless someone has a great deal of information available (like pressure trace data helping nail down the start pressure), there is something to be had by excluding loads that cannot be on a node. For what it's worth, I've done all of my testing to date with jumped bullets. I am preparing to test a jammed load and see what happens. In my case, I am not trying to predict the results before shooting. I am, instead, looking at the results and trying to determine if there is a pattern to those results.

So to answer the OP question: In my opinion, No, not necessarily.