Accuracy Node???

[CaptnC]

While I guess I should have thought back to my hot rod'n days...when you speed could be the same as another guy but you beat him by by a quarter of a second...

Velocity doesn't equal time traveling in the barrel.

okie man...it looks like I'm finding that to be the case as well. I've used it in a couple calibers...none have shined like I hoped.

In the Hodgdon powder site you can input a bunch if info...caliber, bullet, powder manufacturer and leave the powder set at "All" and it wI'll give you all the powders that work for a given caliber/bullet weight...Hybrid 100V comes up a lot.

 

[1Moose]

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.

Coincidentally, my new project is finding preferred loads for a 260 Rem I recently had built. I'm looking for the level of results you found for yours (using either Berger 140 VLDH or Hornady 143 ELD-X) and have more work to do. I had a bunch of 4 and 5 shot groups at / just under an inch at 200 yds, but I want to cut that to 1/2 inch at 200 yards so I can be 1 inch worst-case on a "bad" day. You've given me a benchmark!

 

[shphtr]

I have often noticed that for a particular rifle the most accurate velocity will often be "about " the same even with different powders, the difference is that one or sometimes two powders at this "optimal velocity" will be more accurate then any of the others. To support this point look in a reloading manual that will annotate the most accurate load for a particular caliber with different powders - the most accurate loads with the different powders are usually all pretty close (usually within 50 to 100 FPS).

 

[TheDude270]

I can't speak to the exact physics but so far nodes are directly related to velocity in my 270win from powder to powder. Sure I get better accuracy with one powder over another but the nodes seem to be right on with same velocity figures. As stated above, might at least not be a dumb thing to do when new load development, to match velocity of previous good loads.

 

[Mike 338]

I've never bought into a node being at a specific velocity. A couple tenths of a grain can open things up a fair amount. I would think that if you wanted to do a quick and dirty comparison between two powders, load up 15 or 20 of each powder in .2 grain increments and chronograph them to find the node of lowest extreme spread. Pick your best nodes for each and load up a string of each and give'em a try. Magneto Speed is good for this because you can literally pull off the side of the road and shoot into a bank of dirt to get you velocity data, then go back home and make some real loads for accuracy testing.

 

[MagnumManiac]

After extensive testing with a pressure trace and chrony, a node is simply all about EQUAL BARREL TIME. The VELOCITY at which this occurs really has nothing to do with it other than ALL velocities within THAT LOAD need to be close to each other to get the precision we are looking for.
A different powder will produce different barrel time even at the same velocity. Looking at pressure curves tells you a lot, if start pressure fluctuates wildly, often the ES is off the chart, BUT it has been noted that even with 100fps ES, a load can shoot tiny groups at CLOSE RANGE because the bullets exit at the same still point in the barrel vibration. Shoot this same load at 500 and you will have 2 distinct groups due to vertical dispersion.
There is no set rule that the barrel time of one powders velocity is going to be at the same point in barrel oscillation just because the velocity is the same. Different powders rise to max pressure differently and accelerate the bullet at different rates, therefore barrel time is different.

Cheers.

 

[TheDude270]

After extensive testing with a pressure trace and chrony, a node is simply all about EQUAL BARREL TIME. The VELOCITY at which this occurs really has nothing to do with it other than ALL velocities within THAT LOAD need to be close to each other to get the precision we are looking for.
A different powder will produce different barrel time even at the same velocity. Looking at pressure curves tells you a lot, if start pressure fluctuates wildly, often the ES is off the chart, BUT it has been noted that even with 100fps ES, a load can shoot tiny groups at CLOSE RANGE because the bullets exit at the same still point in the barrel vibration. Shoot this same load at 500 and you will have 2 distinct groups due to vertical dispersion.
There is no set rule that the barrel time of one powders velocity is going to be at the same point in barrel oscillation just because the velocity is the same. Different powders rise to max pressure differently and accelerate the bullet at different rates, therefore barrel time is different.

Cheers.

Makes complete sense. Difference between RL-19 and H4831sc, different barrel exit times regardless of velocity at 15 yards past barrel. However, I still am noticing that as I conduct tests I'm able to ball park guess (SO FAR) based on velocity and seeing as though that is the easiest thing for people to correlate, especially people who haven't read up on internal ballistics, it's an interested aside I think; to notice 3 load tests with same bullet different powder and all seem to happen around same velocity. I see what you're saying, that there is no set rule for a velocity correlation. My testing has been extremely limited too compared to anyone on this site.

 

[gohring3006]

After extensive testing with a pressure trace and chrony, a node is simply all about EQUAL BARREL TIME. The VELOCITY at which this occurs really has nothing to do with it other than ALL velocities within THAT LOAD need to be close to each other to get the precision we are looking for.
A different powder will produce different barrel time even at the same velocity. Looking at pressure curves tells you a lot, if start pressure fluctuates wildly, often the ES is off the chart, BUT it has been noted that even with 100fps ES, a load can shoot tiny groups at CLOSE RANGE because the bullets exit at the same still point in the barrel vibration. Shoot this same load at 500 and you will have 2 distinct groups due to vertical dispersion.
There is no set rule that the barrel time of one powders velocity is going to be at the same point in barrel oscillation just because the velocity is the same. Different powders rise to max pressure differently and accelerate the bullet at different rates, therefore barrel time is different.

Cheers.

I agree, it's seen often in a load that is 1/2" at 100 yards and falls completely apart at long range. Also certain powders in certain cartridges have a violent muzzle exit. I refer to it as muzzle exit pressures. I believe this is the reason some have to tweak the BC to get hits. It will upset the bullets stability right out of the gate, but you won't notice until way down range.