I've just done a 15 shot test with increasing increments of powder, looking for the fabled plateaus where SD is fairly low cross a couple powder weights. Question is, why does the plateau occur?
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I've just done a 15 shot test with increasing increments of powder, looking for the fabled plateaus where SD is fairly low cross a couple powder weights. Question is, why does the plateau occur?
I BELIEVE its where the powder cant push projectile any faster ,either its run out of push or run out of barrel to push it in (flame thrower if go any higher)....
To date I haven't found any that couldn't be explained by statistical variation.
It might be a myth then Puffin?
Its true with black powder you could work out the max load by firing over a white sheet. You kept increasing the powder when you noticed black specks on the sheet you had exceeded max load. More wouldnt give you any more velocity but it wasnt dangerous it just didnt have time to burn before the bullet left the barrel.
Attachment 96988
The column on the lower left, is that the kind of thing you are looking for.
Yes, Cowboy that's what I mean. The theory that at certain ranges of powder charge velocity changes very little. Like this graph from the 6.5 Guys. They say we should focus on loads where the line is flattest since there, the SD is lowest. I don't know enough to dispute it but I can't get the idea to reconcile with anything I know about physics. Thought I'd ask if anyone else knew what was going on.
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What is the correlation between the plateau of the velocity and the stabilisation of the barrel harmonics?
Can you have regular speed and shitty groups? And very good groups but very irregular speed?
Does "SD" refer to sectional density? Is that not just basically a formula for bullet weight over bullet frontal area, unrelated to velocity?
I'm guessing SD means standard deviation.
Could the plateaus be where the extra powder (and it's energy) are going into your brass instead of more velocity? As in the extra energy is stretching/deforming/working the brass more?
If you are shooting one shot at each powder weight, then repeat the exercise and see if it gives you the same or different results.
I’ve done it on heaps of rifles. Most of the time it works just fine. It gives you a pretty good idea of where to concentrate your 3 or 5 shot groups at the desired velocity depending on case pressure. You can also find your max pressure. Keep going till primers flatten and velocities usually peak then decrease 20 FPS. Adjust seating depth to increase accuracy. Not all nodes give good es. Or accuracy. Some people shoot 2 at each charge. You still get the same idea. It’s about speeding up simplifying and using less rounds for load development. I’ve found more often than not 1/2” or less single digit SD loads in 10-12 rounds. And tweak from there.
Thank you Cowboy06
Interesting observation. Never thought of why there would be flat spots in velocity, just that they are beneficial to identify and work with. I cant find any indication as to why on dr google.
If you think about it logically there is no way to gain any reliable indication of a plateau by using one shot per charge weight. The usual ES of most loads will make it completely random. @stug is on to it, if you think you have found something repeat the test twice more.
read up on Dan Newberry's Opitmum charge weight, and Chris Longs's optimal barrel time
OCW Overview - Dan Newberry's OCW Load Development System
Optimal Barrel Time Paper
velocity "usually" flattens out at the accurcy nodes...but not always so go figure!
1000yd tuning, positive compensation, ladder tests, ladders for seating depth...
So many theory's so little barrel life.:yaeh am not durnk:
Truth...Quote:
Originally Posted by sneeze
Do it this way, don’t do it this way, try it yourself. All I know it works most of the time quickly. The odd projectile or rifle takes a little more tweaking. At the end of the day everyone would arrive at the same load with the same rifle however you do it. This way is just the quickest, least hassle, least rounds and least barrel life used.
I had a guy come out to see me to do load development on a creedmore. 35 rounds later he had gone from 2350 FPS to 2500 FPS and was still at least 200 FPS off his target velocity. Like watching grass grow. Took about an hour and a half by the time he let the barrel cool between strings.
I have tried it. After shooting the first string I shot a second, the plateau from the first string wasnt there in the second. I could have shot the second string first, or third. It did give me an idea of where max might be but that's about all. I posted similar results here https://www.nzhuntingandshooting.co....38/index2.html
Iv Had a good look at barrel timing and that comes with its own set of issues. I ran some of my best loads through the theory and got noting but random results. Trying to use QL to determine the exit time is hopeless, its just computer modeling and there are to many variables to expect any consistent level of accuracy from it. That shows in the random outputs compared to real worl results as well eg fro my 243ai its right on the money but the 280ai its not within 150fps with any of the loads I tried.
The OCW I think works ok but its not far off a what Id call a stanard work up.
My opinion fwiw is these techniques are mostly smoke and mirrors that become accepted through a combination of confirmation bias and to small test samples.
But its little more than an opinion so ..
I have worked up loads for a lot of rifles over the years and find the Dan Newberry OCW quite helpful but experience usually lets me spot the load that's going to work in each rifle. It's a bit like when your hunting a new area and you move into a spot and it just screams an animal is here! I know this doesn't help someone who has done little load development but thats just how it is.
Sneeze, I saw your results. 1/2 grain is too much. You’ll never see flat nodes. .2 to .3 to get accurate node data. But what ever do it your way, I’ll do mine. If your going to shoot 3 shots at each you might aswell shoot groups.
The example from the other thread is a large 7mm. .5gr is smaller than your .3 in a creedmore in percentage terms. When I tried it I used .2 in 222 rem. I’m not saying there is no flat spot but statistically you can’t find it from one shot per charge. Think about the variation you get from one three shot group. It can easily be 30fps. You don’t know if your single shot is the high value low or close to the average. The high from one followed by a low from the next and it will look flat but reverse that and it will show a the opposite. In order for the theory to work every single shot would need to be close to the average. It won’t be so it becomes random.
But yes by all means we are free to believe in anything we want .or not. If it’s working for you and is repeatable the 👍
