HELP WITH SATERLEE VELOCITY TEST

[Chase723]

Having measured engraving pressures on numerous small call bullets, I can tell you that velocity consistency is limited by shot-to-shot variations in bullet engraving pressures. Are there can combinations of powder/primer/projectile that give low velocity variations? Sure there are. Doing a single shot ladder test is a sure way to get fooled about which combination gives the lowest velocity variation & smallest groups. I'll say it again: velocity "nodes" determined by a single shot ladder test are meaningless.

It's worth shooting a ladder 2 or 3 times for confirmation as mentioned by several people in the thread.

 

[AaronSkipDavidson]

I wonder where all the powder and primers are going! ;-)

 

[WildRose]

Velocity "nodes" are an artifact of small sample size & non-zero shot-to-shot variations in bullet engraving pressure. They're totally meaningless. Don't use them

Ok I'm curious, based on what exactly?

 

[Opa-lopa]

A cursory knowledge of statistics & 40 years of experience as a ballistics engineer.. www.Bulletology.com

 

[WildRose]

A cursory knowledge of statistics & 40 years of experience as a ballistics engineer.. www.Bulletology.com

That doesn't answer my question.

With a given load the engraving pressure is going to be very consistent or should be at least until the bore gets really dirty.

 

[Opa-lopa]

That doesn't answer my question.

With a given load the engraving pressure is going to be very consistent or should be at least until the bore gets really dirty.

I measured Engraving pressure variation in small cal bullets 20 years ago for the government. The variability (sigma) is a MINIMUM of 5% of the peak engraving pressure, that causes a muzzle velocity change of 10 FPS. As a reloader, the variation in this is something out of your control. So 95% of your bullets will have a + - 20 FPS swing at any given charge weight. Go look at my website at the 2004 precedings reference.

 

[WildRose]

I measured Engraving pressure variation in small cal bullets 20 years ago for the government. The variability (sigma) is a MINIMUM of 5% of the peak engraving pressure, that causes a muzzle velocity change of 10 FPS. As a reloader, the variation in this is something out of your control. So 95% of your bullets will have a + - 20 FPS swing at any given charge weight. Go look at my website at the 2004 precedings reference.

Considering how many people I know shooting loads with less than a 20fps ES I find that rather hard to accept as factual.

 

[Veteran]

Looks to me like you have a flat spot where velocity does not change a lot around 52.5 gr at 2905 and 52.7 at 2908.

A Possible higher node would be 53.9 at 2988 to 54.3 at 2985.

I would load at 54.3 and work down with 3 shot groups at .1 gr reductions to see where they group best,
and I would start at 52. 7 and do the same going down with 3 shot groups.

I don't like using a magneto speed when I run Satterlee because it will shift POI and may also affect velocity.
It certainly will affect where the barrel tip is pointing and the harmonics.

You could run an Audette Ladder at 300 and even run this test at 200 or 300 to get more definition on POI
at distance. These flat spots are just places to further tune from in 3 shot groups in my book. But you have to do that without the weight hanging from your rifle bbl or you will never get anywhere in real life at the bench or hunting because that
magneto speed wont be on your bbl then. Best to run Satterlee and start using a regular Chronograph or Labradar if possible.
Just my druthers......Good Luck.

 

[WildRose]

View attachment 341034

Looks to me like you have a flat spot where velocity does not change a lot around 52.5 gr at 2905 and 52.7 at 2908.

A Possible higher node would be 53.9 at 2988 to 54.3 at 2985.

I would load at 54.3 and work down with 3 shot groups at .1 gr reductions to see where they group best,
and I would start at 52. 7 and do the same going down with 3 shot groups.

I don't like using a magneto speed when I run Satterlee because it will shift POI and may also affect velocity.
It certainly will affect where the barrel tip is pointing and the harmonics.

You could run an Audette Ladder at 300 and even run this test at 200 or 300 to get more definition on POI
at distance. These flat spots are just places to further tune from in 3 shot groups in my book. But you have to do that without the weight hanging from your rifle bbl or you will never get anywhere in real life at the bench or hunting because that
magneto speed wont be on your bbl then. Best to run Satterlee and start using a regular Chronograph or Labradar if possible.
Just my druthers......Good Luck.

We're seeing about the same thing I think.

Personally I'd look to see if there's an accuracy node coinciding with any or all of them.

 

[Veteran]

I've simulated a OCW/Satterlee/Ladder test in the graph below. I used Excel to randomly generate a velocity within the normal distribution one would expect with a muzzle velocity standard deviation of 10 fps. To get the velocity at each charge weight, I took the OP's data and regressed a line through it, which came out to a slope of 55 fps per grain of powder. I then used the OP's 0.2 grain charge increment to calculate the nominal velocity at each increment, applied the random variation, and ran the simulation 4 times.

I circled all the "nodes" for emphasis...

So...see if you can pick out the OP's data from the randomly generated data...

View attachment 207777


If it's not clear, OCW/Ladder/Satterlee etc are usually an exercise in interpreting random noise (seeing faces in clouds or reading tea leaves). It's plausible that they may have some merit for the absolutely most precise ammunition and rifles, or perhaps if one were to fire 10 shots at each charge weight to achieve reasonable statistics.

Yes you are right. This is randomly generated statistical noise. I can't tell anything from it. Statistically every person has 1 testicle and 1 breast on average. Running a Monte Carlo is totally random. So random is what you did. I think the point you are trying to make is that the flat spots are just statistical aberations which depend on how the randomness lands on the standard deviation of the ammo you are using at each charge. The key is whether your random curves are repeatable each time you run them and they won't be, because the Monte Carlo will be random and do something different next time.

I don't believe a real rifle system is that random--- though the ammo may be somewhat random, especially if its not a high quality ES and SD ammo. There really is no point running a Satterlee or Audette, or anything concerning tight groups as a goal with High ES and SD ammo. And I believe getting a 150 fps spread at a given charge weight say at data point 12 for charge weight from one series to another is not with the realm of the real world. Something pretty random about that for sure...........

The good advice you gave was to fire more rounds at each charge weight. The whole purpose of the Satterlee in particular though is to save ammo and try to get some charge weight ranges to work from up and down until you get repeatable results with tight groups. If you are going to shoot as many as 10 rounds at each data point to get a statistical average for each data point, it defeats the purpose of trying to narrow down to a range to work from before shooting more ammo to examine grouping and repeatabiity.

I ususally shoot 3 rounds at each charge weight which is a compromise but its better than 1 and not as time and money consuming as 10.

The goal of a Satterlee is not to get a final answer so its not going to be statistically the test to run for significance.
To me, its to get rough ranges that show some promise on velocity sweet spots where velocity does not vary a lot over some
range of charge weight so that there is forgiveness, in where the bullet will hit at a distance if the charge weight is off a little here or there. In that regard it is similar to Audette Ladder in being forgiving of the vertical dispersion out at 300 yards even with slight charge weights. Satrerlee nodes are good places to work from for more fine tuning until one does get repeatability and tight groups.

 

[DUSTY NOGGIN]

I measured Engraving pressure variation in small cal bullets 20 years ago for the government. The variability (sigma) is a MINIMUM of 5% of the peak engraving pressure, that causes a muzzle velocity change of 10 FPS. As a reloader, the variation in this is something out of your control. So 95% of your bullets will have a + - 20 FPS swing at any given charge weight. Go look at my website at the 2004 precedings reference.

have some questions , very curious regarding your testing processes

can you please explain your testing process in as much detail as you can , how did you maintain the constant pressure for your testing ,maybe how the test separated things like gas seal at neck, ignition, precise internal volume, bullet construction/ type , barrel material , to return only the engraving data . how did the testing eliminate any cartridge variations to get only engraving data , and processes were done to keep any cartridge variations away from the results , what powders did you use and did you do any testing with medium or magnum cases or larger calibes

fwiw , after doing a few workups like this , i dont think 10 round tells anywhere near enough either besides maybe max pressure , i would however at this point in my learning that id have to disagree that im limited to a 20 fps swing based off engraving alone, but i have been working with larger diameter projectiles maybe that is true with 22 cal projectiles , dunno ??