HELP WITH SATERLEE VELOCITY TEST

[25WSM]

Looks like you got that Creed shooting great. I love how easy it is to tune the 6.5 Creed. It's just not to dang picky at all it seems. I've tried at least 6 different powders in my 6.5 Creed's and they all worked real good. I have yet done a Satterlee test that didn't show me nodes to explore. Someone said it only works with H extreme powders but that's not the case for me. To me it's just too simple to not do. Even if it didn't show you a node it shows you where your max load is for the combo your trying.
Shep

 

[WildRose]

Well, to what do you attribute the variation then?

Brass, brass prep, primers, bullet, seating depth are all the same (or should be). The only variable you are introducing is powder charge.

Either the powder burn stutters in certain places giving velocity nodes, or it doesn't.

Please tell me what causes this. If it isn't a random artifact of overlapping ES, then what is it? How is it caused?

Inconsistent primers would be the first place I'd look, some fouling of the powder would be next if the variations are outside those what are to be expected in temperature variations. Some powders are much more temperature sensitive than others.

Even the difference in having your ammo exposed to the sun vs shaded can make a big difference in moderate temps. In very cold temps keeping it warm next to your body vs in a cold chamber can induce some pretty serious variations in velocity as well.

 

[WildRose]

Final follow up. Like @25WSM said, do what the rifle tells you and what works for you in a methodical way. Satterlee method works for some people. Fortunately, I'm one of them. This is the result of the load I just developed using it for the 6.5 Creed I mentioned in my last post. 1" and 1.28" at 525, shot back to back. I know they're only 3 shot groups but the ES from the velocity data for 7 rounds over 41.2-4.16gr was 15. So I suspect that it'll be around that, and maybe a little better.

Well done.

 

[WildRose]

Dang it, got me again... .

 

[Opa-lopa]

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

 

[Chase723]

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

To the contrary. Pressure/velocity nodes are meaningful. Why do you think that certain loads, or derivatives very close thereof, are almost universal for several cartridges? Furthermore, loads that are not within a velocity "node" by definition have large velocity variation and will perform terribly beyond ~500 yards. Why do you think that all serious shooters will pretty much reject all loads with an ES >30, and many will only accept <20?

 

[Opa-lopa]

To the contrary. Pressure/velocity nodes are meaningful. Why do you think that certain loads, or derivatives very close thereof, are almost universal for several cartridges? Furthermore, loads that are not within a velocity "node" by definition have large velocity variation and will perform terribly beyond ~500 yards. Why do you think that all serious shooters will pretty much reject all loads with an ES >30, and many will only accept <20?

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.

 

[ntsqd]

I wouldn't call them meaningless, I would call them indicative of the regions that need further exploration. Some of those regions may well prove false, but not all of them.

At some point the desire for data has to be offset by the need to preserve the barrel's life for it's actual intended use.

 

[Opa-lopa]

Meaningless. There's a 5% MINIMUM variable engraving pressure shot-to-shot that causes about a 10 FPS swing in muzzle velocity for the same charge weight. The ONLY way to find out what a given charge weight does is to fire a larger sample. A single shot at one charge weight gives you a muzzle velocity that could easily be higher or lower by a significant amount. In a single shot "ladder", you'd be far better off looking at all the velocity data and drawing a line (least squares fit) thru it. Power weight is energy, how could you possibly put more in & not get more MV out in the long term?

 

[ntsqd]

I'm not a student of internal ballistics, but I do know that it is possible because it happens. Charge weight vs. MV is NOT linear relationship.

 

[redneckdan]

Someone said it only works with H extreme powders but that's not the case for me. To me it's just too simple to not do. Even if it didn't show you a node it shows you where your max load is for the combo your trying.
Shep

Same here. Have had great results with Ramshot powders.

The single round per charge work up is just the start of the process. I'm looking for regions where shot to shot variation is lesser than surrounding regions. Those regions are then explored more in depth.

I have had experiences where I find loads that didn't work, good ES but the accuracy wasn't what I wanted. It is far less frustrating to me than finding a really accurate load at 100yds with horrible statistics. I have a cold weather .223 load like this. Excellent 100yd accuracy but horrible ES and high variance with temperature. It useless for extended range practice but dam if it doesn't shoot bug holes at 100...

 

[Opa-lopa]

I'm not a student of internal ballistics, but I do know that it is possible because it happens. Charge weight vs. MV is NOT linear relationship.

For the small changes we're talking about, it's very close.

 

[ntsqd]

Very close is still not linear.

I think that we'll have to agree to disagree. You're not going to convince me of anything, and I'm not going to try to convince you of anything.

 

[25WSM]

Ive had extremely good luck with finding nodes like this. I shoot every gun i build to make sure it performs. I dont have all day to do load development. I can do one velocity ladder and pick the best node. Then do a quick seating test. And then get 1/2 moa out of it. Thats as far as i take a customer rifle. With that load they can tweek it to do better. If it didn't work I wouldn't do it. But it works perfectly for me.
Shep