Accuracy due to velocity, charge, or random...?

[entoptics]

Disclaimer. I'm an experienced reloader, and know all about the "every rifle/bullet/zebra is different". I also am not much of a believer in "nodes", at least in run of the mill rifles. That being said, I obviously recognize that some recipes shoot significantly better than others in a given rifle.

Anyway, curious about people's experience with the following...

If you get a particular load shooting well in your rifle, have you been able to reproduce the results by matching the velocity, despite switching components/recipe (assuming ES/SD, load density, or burn rate doesn't change drastically)?

For example (and why I'm asking), my 300WM got pretty settled in shooting a 208 ELDX at about 2900 fps using H1000, Fed 210M, and Norma Brass. I've pretty much shot up my brass, so I got a new stash of a Sig brass. It's drastically different in capacity (250 gr vs 215 gr), and as expected, my preliminary testing shows I need to back off my recipe a little to keep pressure/velocity in check. I've only shot a few thanks to 5 feet of snow this month, and accuracy seems fine still, but this lead me to the above question.

Have any of you been even more drastic than my situation? For instance, changing powder/primer/brass, but tuning to get the same velocity as a good shooting load, and having the new load perform well too?

 

[Canhunter35]

Using the same brass/primers/and bullets, I've replicated loads in my 300wby using h1000,7828, and 7977 around 2800-2850fps.
Nodes definitely exist, but changing powders and burn rates can change the harmonics and ignition of the bullet, changing where the node is

 

[lancetkenyon]

Cut your powder charge and work back up and check for yourself. If using the same powder, bullet, primer, I bet a slight reduction in charge weight will bring you right back in once you get the brass fire formed to your chamber. I know some of those belted magnum new brass have significant headspacing. Like .020" sometimes.

 

[ar10ar15man]

a gun is "shooting system".
change any part and the results change.
if it has a free floated bbl, it has nodes whether you believe it or not.
what you are describing is tuning to a node.

 

[cajun]

Accuracy nodes do exist. If you change any component you need to rework the load. Different powder lots also.

 

[entoptics]

All the rifles I've loaded for are factory, though the 300WM in question has a Shilen barrel installed. I've never found a "node" for any gun, in the dozen or so times I've tried it. I've found recipes that work better than others, but only large variations have affected measurable precision. For instance changing the bullet type, big changes in powder load density, or huge changes in seating depth.

None of my rifles are bug holers though. About 3/4 to 1 MOA is all I've ever gotten out of them (on average, not "that one group that one time"). Perhaps someday I'll get a Ruger American in 6.5 Creedmoor, and then I can tune it to a "node" and take it from 0.25 MOA down to 0.1 MOA. At least that's what I read on the interwebs...

@lancetkenyon. The new brass is definitely WAY shorter. Shoulder datum is 0.01" shorter than once fired. This has been my experience with Winchester, Norma, and now Sig. They sure do rely on the belt for headspace when they make those puppies. Factory ammo tends to measure similar too. I usually run the shoulder down about 0.002" when I resize after the first firing.

I'll do some experiments with the new brass, and see if I can get the same accuracy as before, just by tuning the load down to the same speeds. Preliminary data indicates about 2 grains less of H1000. Hopefully going out tomorrow. 20°, but at least it won't be snowing, and the wind should be calm...

 

[FURMAN]

I have to laugh a little because in other threads you have acted as if you consistency shoot .1 groups and know all about tuning. Nodes absolutely exist and certain bullets prefer certain speeds from certain barrel lengths. If you really care to learn about tuning you would follow what 1000 yard BR guys or Fclass guys are doing. One of many examples is the 300 wsm with 210 VLDs or 215 hybrids will have a node around 2850-2900 from a 28-34" barrel. I have found that typical nodes are 20-50fps wide and about 100-150fps apart. It is going to pretty hard to see, in my opinion, from a rifle only capable of .75-1moa.

 

[entoptics]

I have to laugh a little because in other threads you have acted as if you consistency shoot .1 groups and know all about tuning.

You don't read well, or at least don't retain information well. You will find nowhere on this forum, or anywhere else, that I've ever claimed 0.1 groups. I have a spreadsheet with nearly 100 measured groups, and my personal best is 0.33 MOA. There's only 84 posts outside this thread according to my ticker, so I encourage you to revisit them, and then retract your sarcastic insult publicly, so that I may "laugh a little" at something that actually happened...

Regarding my knowledge of tuning, I have tried most of the well known strategies multiple times in multiple guns, and have never been able to find a "node" recipe.

It is going to pretty hard to see, in my opinion, from a rifle only capable of .75-1moa.

Which is what I have actually said before. In fact, I pretty much said it in both of the posts in this thread, but since you clearly have trouble retaining information you read, it's understandable you didn't notice it...

 

[ar10ar15man]

well something is holding back your education.
the first thing that is obvious is saying nodes do not occur.
your inability to understand bbl harmonics/vibration and notes is the first step you need to address.
or maybe you just build so-so rifles and they just do not respond like a precision rifle.

 

[entoptics]

well something is holding back your education.
the first thing that is obvious is saying nodes do not occur.
your inability to understand bbl harmonics/vibration and notes is the first step you need to address.
or maybe you just build so-so rifles and they just do not respond like a precision rifle.

Sigh.

1) I've never said they don't exist.
2) I suspect I have similar knowledge of harmonics to you, unless you're actually an engineer or physicist.
3) I don't build rifles, unless you count AR15s and slapping a drop in Shilen barrel onto a Savage LRH...

Would it be possible to get back to the substance of my original inquiry now? Or would folks prefer to keep valiantly defeating straw man caricatures of my opinions?

 

[FURMAN]

In my experience, which is quite a bit, a bullet likes to run at a certain velocity in a certain length barrel which I already stated. The nodes are typically as previously stated. In some cases a slower burning powder will help you get to the next node where as the faster burning powder may have already pressured out. In the cases where you have found a load with new brass and then run out of new brass and start using once fired I have found sometimes you have to reduce powder charge to get back to the original speed(where the node is). Changing brass to a different capacity(brand) will be similar. I have found in magnums when the barrel speeds up you typically have to reduce powder charge to get back to the same velocity as before(where the node is). Some just ride the extra velocity at the expense of loosing accuracy. I will take accuracy over velocity every day but velocity is a consideration when choosing a cartridge.

 

[ar10ar15man]

i think i answered your question in post 4

 

[Almondgrower]

Find your pressure cealing and shoot 5 , 5shot groups backing powder charged down 1-2% per group . You will more then likely find a standout node , then start playing with seating depths to (tune) the load , it is important to shoot in a round robin type sequence so as the barrel fouls it does not alter testing , keep barrel heat to a minimum also

 

[Almondgrower]

http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134

This will be very helpful in potentially taking you hand loads to the next level .