I am thinking about saving my bullets, powder, and primers, I don't need to get all the speed available out of any given cartridge. But I would like to get to a high point in the vibration cycle and get a good chance on an accurate load. In days gone by I would start a grain or grain and one half above min and go to max. I am tuning a 308 win load that Nosler gives for their 125 grain BT, with WIN 748 how many grains would I have to go to find the top of the barrel travel. I guess what i am asking is how many .01s does it take to get one complete cycle. Is this question even answerable?
How many grains from node to node?
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searcher
Gold $$ Contributor
I first try to find a powder that seems to like the bullet and rifle combo AND I want to be able to get good accuracy at the speeds I do want it to shoot at. Some nodes will be very "short", and others VERY "wide", depending on the powder used with a particular bullet. How your rifle will react to that bullet and W748 is only a guess, though maybe you have already shot some out of it? I'd start at the bottom of the ladder, shooting only 4-shot groups and jumping 3/10-4/10 in grains per group. The logic being I don't want a node so narrow that a few tenths of a grain can take me in or out of a reasonably good group. So, it makes no sense (to me) to try to fine-tune a load from the start with powder that may not work at all. If I want to shoot in the mid-range of the load data and I get no reasonably good groups out of the 4 or 5 groups (typically ranging about 2 to 2 1/2 grains) I shoot, I move to another powder. If you are determined to use the W748 and will be satisfied with the best groups that you can get out of it at a certain powder setting, I'd run all the way up until you start seeing signs of pressure. While it is not necessary to run until you see signs of pressure, I do so, so that I know that a load I may settle on if it turns out to be near the top isn't going to surprise me when the weather gets hot. If I have backed off a full two grains after the first hint of pressure, for example, I'd feel a lot safer if you are not set on attaining the highest velocities. Likewise, I think a lot of guys don't start all the way at the bottom of the recommended ladder and sometimes miss the "killer" node that happens to be low velocity. I have one particular varmint rifle that I shoot surplus Military powder with, and it is a slow, dirty load. Far below the velocity I want to shoot at, but it puts the bullets in one hole, is a safe load to shoot from freezing to 110 degrees and still puts them in one hole through that range. All said, I'd think you'd want to shoot maybe 20 rounds to test powder and more to fine-tune as need be. I'd also tend to initially seat varmint bullets at the factory recommended OAL as I've found that, more often than not, they tend to like to jump a bit more than I was accustomed to shooting target rifles and bullets. If you are getting 1" groups in a rifle you know capable of doing half that, for example, I'd either change the bullet or powder. Lots of different methods used to do all of this.
I venture the answer to this will depend entirely upon how a shooter is defining what is a node. Not sure what the answer will be for the shooters which follow modern revelations in ballistic science as to why long standing hypotheses have failed to have been proven, such they'd subscribe to the premise that there are no nodes...
6.5 forever
Silver $$ Contributor
I believe that any NODE is only good for the day it was tested. My node testing showed constant changes.... I now save my testing components for practice on wind and lighting changes. If there are really nodes, why do we need scales that measure to tenths of a grain? But I am not a ballistic scientist....
We use accurate scales to control the variables we can readily measure. Just good practice and the eternal search for improvements.
jds holler
Gold $$ Contributor
I like the idea of it being an X% figure, but 3% seems to be a pretty large amount, for instance 1.2 grains on a 40 gr. charge weight. Seems like a guy might cruise right on past a great node if you jump that much at a time.
If the node is based upon barrel vibration or "whip", I could imagine it being different depending on a bunch of factors -- barrel weight, diameter vs caliber, barrel length, PSI, barrel temperature, muzzle device, twist rate, bullet weight, powder burn rate, -- good Lord, how could we ever hit a node
jd
If the node is based upon barrel vibration or "whip", I could imagine it being different depending on a bunch of factors -- barrel weight, diameter vs caliber, barrel length, PSI, barrel temperature, muzzle device, twist rate, bullet weight, powder burn rate, -- good Lord, how could we ever hit a node
jdGuess you have trouble with your rifle holding zero then?
Nothing is gospel in my book.
6.5 forever
Silver $$ Contributor
Nope.
tom
Gold $$ Contributor
I'm a 3% guy, and it's usually real close to that. Experience limited to using ladders at distance as Charlie mentions above.
I've seen the same thing from 21" sporters to 34" 1.450s, and barrels with tuners on and off. It seems we tune powder by pressure and not so much speed, is what that tells me.
Pretty simply find max - work down covering at least that much - if it sucks then change powders and start over.
Tom
I've seen the same thing from 21" sporters to 34" 1.450s, and barrels with tuners on and off. It seems we tune powder by pressure and not so much speed, is what that tells me.
Pretty simply find max - work down covering at least that much - if it sucks then change powders and start over.
Tom
You’ve done excellent research up to this point. Nosler lists 748 as top accuracy with 125 gr.
Charge weight range is narrow for this combination. I’d start at bottom and move up .3 gr at a time, then more granular up or down once node identified.
www.nosler.com
Charge weight range is narrow for this combination. I’d start at bottom and move up .3 gr at a time, then more granular up or down once node identified.
308 Winchester Load Data
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Larry Koch
Silver $$ Contributor
If that is what you are finding, then you have the wrong powder or other issues going on. When you are using the optimum powder for your case/bullet combination, and at a reasonably close seating depth, you should find a very repeatable load that shows up like a stable consistent girlfriend. When the combination is wrong...it will be like dating a girl with multiple personality disorder; you won't know who will show up at the door on any given date night. I've got the T shirt.
When you guys state 3%, are you talking about 3% differences in charge weight?
Meaning that if I find a load that my rifle likes using a specific bullet and a specific powder, going up or down approx. 3% in charge weight with that same bullet and powder will put me in the range for a similarly performing node?
Am I understanding that correctly?
Meaning that if I find a load that my rifle likes using a specific bullet and a specific powder, going up or down approx. 3% in charge weight with that same bullet and powder will put me in the range for a similarly performing node?
Am I understanding that correctly?
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