Accuracy Node???

[CaptnC]

I was shooting my newest creation (6.5-284) over the weekend. It seems to me that "the node" is velocity related from reading between the lines on most threads relating to this topic.

I loaded two different powders Hybrid 100V and H4831sc...the H4831sc load was a recipe I found on this site as a known highly accurate load. Judging by the velocity of that load it tried to copy the velocity with the Hybrid 100V.

The velocity of the Hybrid was below the H4831sc and was pretty much everywhere. The H4831st did as predicted and made me look like I know how to shoot out to 600yds!

The velocity are close. I wonder if I bump the charge up 0.3 grain or even 0.5, that should be enough to bump up the speed to match the H4831sc load?

Both loads are well below max...for once I want long range accuracy and not looking for a laser beam.

I know what the first question is going to be...why bother? If the H4831sc shoots so well, why bother?

To test the theory if the velocity is correct, the powder is only the means to get that velocity/node.

ES was good on the H4831sc too...even with my cheap chronograph. My three shot group at 600yds was between 3 and 4 inches...I wish I had walk down there and took a picture. But it was super muddy and there is a huge mud hole in front of the 600yds steel...so all I got was a cell/spotting scope photo...and that was captured out of the middle of the video.

 

[gohring3006]

I'm not exactly sure of your question. But I'm thinking you are asking if the accuracy is at a certain velocity, then getting to that velocity with any powder should produce the same result..
Right?

If so, muzzle exit pressures come to mind as one of the first influences on your theory.

 

[Greyfox]

I have seen choice of powder make a difference for a given velocity. Not sure whether it's due to burn characteristics, effect on barrel harmonics, etc. I exactly matched the velocity in one of my 6.5x284's of 2970FPS using 57gr of Retumbo and 54gr of Reloader 26. Both used with Lapua Brass, Fed210M, Berger 140HVLD at the same seating depth, same day. Velocity and ES were the same, however in my rifle, Retumbo which has.and continues to produce sub .5MOA groups is noticably better then Reloader 26 which was .75MOA, best case. Reloader 26 may very well have a different accuracy node which I haven't explored yet.

 

[Pdvdh]

I think there are so many affecting factors involved that only God knows the result ahead of testing on paper.

 

[CaptnC]

gohring, I guess my post was a bit too long...

But yes that is my thinking.

After I posted this I got to thinking...just the nature of the ignition from one powder to the next, one being more intense than the other will cause the speed of the "wave" to change.

I guess I should have thought about it more...I was setting my 6.5-284 die up yesterday and got to thinking about it.

The Hybrid shot so bad I only fired about a dozen so I was thinking about pulling them apart to save components or bump the charge up a hair to see what happens. Because it's in a scatter node right now.

 

[gohring3006]

gohring, I guess my post was a bit too long...

But yes that is my thinking.

After I posted this I got to thinking...just the nature of the ignition from one powder to the next, one being more intense than the other will cause the speed of the "wave" to change.

I guess I should have thought about it more...I was setting my 6.5-284 die up yesterday and got to thinking about it.

The Hybrid shot so bad I only fired about a dozen so I was thinking about pulling them apart to save components or bump the charge up a hair to see what happens. Because it's in a scatter node right now.

Seems to me, I've always had narrow nodes when working with over bore cartridges. I have never messed with the 6.5x284 but 7 mag and 300 Weatherby always had a narrow node in my two rifles.
I could literally see dramatic results with .3 grain charge increases. I am in no way informed enough to comment on your particular cartridge.
Good luck

 

[Engineering101]

captnc

Check out this paper written by Boeing engineer Chris Long. It explains all this stuff.

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

Bottom line, matching the velocity of a known good load when producing other loads isn't a dumb thing to do because it might work but you'd be better off running a Quick Load analysis, which will give you the barrel timing of the known good load - which is what really determines the location of accuracy nodes.

 

[CaptnC]

Yes Sir gohring, from what I've seen even scatter nodes seem to be very narrow. That why I was thinking a slight increase would get me out of it.

 

[brentc]

Yes Sir gohring, from what I've seen even scatter nodes seem to be very narrow. That why I was thinking a slight increase would get me out of it.

Since you're talking scatter node. If you truly identify it, a simply calculation of the scatter charge x 1.015 will get you into the accuracy node.

 

[okie man]

Some powders are just more accurate than others.in my experience hv100 has proven to be one of the least accurate in the guns and cartridges I've tried it in. On the other hand h4350, varget and imr4064 seem too shine in most others

 

[1Moose]

captnc

Check out this paper written by Boeing engineer Chris Long. It explains all this stuff.

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

Bottom line, matching the velocity of a known good load when producing other loads isn't a dumb thing to do because it might work but you'd be better off running a Quick Load analysis, which will give you the barrel timing of the known good load - which is what really determines the location of accuracy nodes.

I need to get Quick Load (on a Mac)! I've been doing without but too many times wish I could use it for a head start.

 

[coop2564]

From what I've read nodes are mainly related to bullet time out of the barrel. Because of different pressure curves affecting velocity, they not tied directly to velocity but time.

 

[Engineering101]

1Moose

QL is pretty helpful getting a head start as you put it. I typically will use it to pick the best powder for a given situation and usually that is the one with the highest velocity and that fills the case (and is temp stable or whatever else you are looking for). I then load a few rounds of a medium low load and go fire them over the chrono. I then put the real world data in Quick Load to tweak the powder burn rate to what I actually got at the range. This allows you to then tweak the powder quantity so the barrel timing lands on one of the nodes for your rifle. Load up that load to shoot groups and maybe a few loads to bracket that one and go back to the range and usually you will get a load that groups tight. You can mess with the load some more if you want but it usually is not necessary. Here is a pic of what I mean by tight for a 260 Rem.

 

[okie man]

accuracy nodes are when the bullet leaves the barrel at a point of time the barrel is at the end of a vibration wave. basicly stationary before moving in the opposite direction . velocity and seating depth can change that point of exit